【单选题】
Once environmental damage ______, it takes many years for the system to recover.
A. is to do
B. does
C. had done
D. is done
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相关试题
【单选题】
We worked hard and completed the task ___.
A. in the time
B. on the time
C. ahead of time
D. before time
【单选题】
I didn't expect you to turn _____ at the meeting yesterday.
A. up
B. to
C. out
D. over
【单选题】
I like the teacher _______ classes are very interesting and creative.
A. which
B. who
C. whose
D. what
【单选题】
When Lily came home at 5 p. m. yesterday, her mother ______ dinner in the kitchen.
A. cooked
B. was cooking
C. cooks
D. has cooked
【单选题】
I don’t know the park, but it's _____ to be quite beautiful.
A. said
B. told
C. spoken
D. talked
【单选题】
Mike is better than Peter ____. swimming.
【单选题】
The young lady coming over to us ______ our English teacher; the way she walks tells us that!
A. must be
B. can be
C. would be
D. could be
【单选题】
Eggs, though rich in nourishments, have ______ of fat.
A. a large number
B. the large number
C. a large amount
D. the large amount
【单选题】
Neither John ______his father was able to wake up early enough to catch the morning train.
A. nor
B. or
C. but
D. and
【单选题】
Jane's dress is similar in design ______ her sister's.
A. like
B. with
C. to
D. as
【单选题】
His salary as a driver is much higher than ________.
A. a porter
B. is a porter
C. as a porter
D. that of a porter
【单选题】
_____ these honours he received a sum of money.
A. Except
B. But
C. Besides
D. Outside
【单选题】
Would you let ____ to the park with my classmate, Mum?
A. me go
B. me going
C. I go
D. I going
【单选题】
I have been looking forward to_____ from my parents.
A. hear
B. being heard
C. be heard
D. hearing
【单选题】
The manager will not _____ us to use his car.
A. have
B. let
C. agree
D. allow
【单选题】
_____ her and then try to copy what she does.
A. Mind
B. See
C. Stare at
D. Watch
【单选题】
Will you ___ me a favor, please?
A. do
B. make
C. bring
D. give
【单选题】
It's bad _____ for you to smoke in the public places where smoking is not allowed.
A. behavior
B. action
C. manner
D. movement
【单选题】
The computer system ____ suddenly while he was searching for information on the Internet.
A. broke down
B. broke out
C. broke up
D. broke in
【单选题】
If she wants to keep slim, she must make a ___ in her diet
A. change
B. turn
C. run
D. go
【单选题】
______ the War of Independence, the United States was an English colony.
A.
B. efore B. At
C. In
D. Between
【单选题】
A police officer claimed he had attempted to ____ paying his fare.
A. avoid
B. reject
C. refuse
D. neglect
【单选题】
While I was in the university, I learned taking photos, ______ is very useful now for me.
A. it
B. which
C. that
D. what
【单选题】
He is not seriously ill, but only a ____ headache.
A. obvious
B. delicate
C. slight
D. temporary
【单选题】
On average, a successful lawyer has to talk to several ____ a day.
A. customers
B. supporters
C. guests
D. clients
【单选题】
What is the train ____ to Birmingham?
A. fee
B. tip
C. fare
D. cost
【单选题】
You shouldn't ______ your time like that, Bob, and was cold yesterdak tonight.
A. cut
B. do
C. kill
D. kick
【单选题】
Both the kids and their parents ____ English, I think. I know it from their accent.
A. is
B. been
C. are
D. was
【单选题】
You had better ___ a doctor as soon as possible.
A. seeing
B. saw
C. see
D. seen
【单选题】
He opened the letter and it contained ___.
A. an important information
B. some important informations
C. many important information
D. some important information
【单选题】
He has been writing for 3 years, but being a writer is not his ___.
A. chance
B. choice
C. change
D. character
【单选题】
They have never heard any ___.
A. a customer complaint
B. the customer's complaints
C. customer's complaint
D. the customers' complaints
【单选题】
He is not a child ___.
A. no more
B. no longer
C. any much
D. any more
【单选题】
The retired man is used to ___ his two dogs early in the morning.
A. exercise
B. exercising
C. exercised
D. exercises
【单选题】
It was not ___ midnight that they discovered the children were not in their bedroom.
A. before
B. at
C. after
D. until
【单选题】
Young ___ he is, he knows how to get along with others.
A. like
B. as
C. although
D. however
【单选题】
Could you show me where the___ shoes are?
A. Women
B. womens
C. woman
D. women's
【单选题】
He succeeded ___ out a lot of things entirely new in the world.
A. in working
B. to work
C. working
D. at working
【单选题】
It took me a long time to ___ the disappointment of failing the exam.
A. get over
B. get up
C. get into
D. get down
【单选题】
She ___ 100 pages of the book today.
A. has already read
B. already reads
C. already read
D. was already read
推荐试题
【单选题】
GPON系统中采用强制（ ）传输方式。 ___
A. 单纤单向
B. 双纤双向
C. 双纤单向
D. 单纤双向
E.
【单选题】
GPON ONU的最大发送光功率是多少（ ）___
A. +0.5db
B. -1 db
C. +5 db
D. +2 db
E.
【单选题】
GPON将业务带宽分配方式分成4种类型，优先级从高到低分别是（ ） ___
A. 保证带宽、固定带宽、非保证带宽和尽力而为带宽
B. 固定带宽、保证带宽、非保证带宽和尽力而为带宽
C. 固定带宽、保证带宽、尽力而为带宽和非保证带宽
D. 保证带宽、非保证带宽、固定带宽和尽力而为带宽
E.
【单选题】
下列对EPON速率描述正确的是： ( )___
A. 上行155M / 下行 622M
B. 上行2.5G / 下行 2.5G
C. 上行1.244G / 下行 2.488G
D. 上行1.25G / 下行 1.25G
E.
【单选题】
GPON标准中目前可以提供上下行对称的速率是 ( )___
A. 1.25Gbps
B. 1.0Gbps
C. 2.0Gbps
D. 2.5Gbps
E.
【单选题】
GPON的最大标称线路速率(下行/上行)为（ ）。___
A. 下行1244.16 Mbit/s，上行155.52 Mbit/s
B. 下行1244.16 Mbit/s，上行622.08 Mbit/s
C. 下行2488.32 Mbit/s，上行1244.16 Mbit/s
D. 下行2488.32 Mbit/s，上行2488.32 Mbit/s
E.
【单选题】
EPON系统根据（ ）来区别流。___
A. GEMPORT ID
B. LLID
C. VPI/VCI
D. Alloc ID
E.
【单选题】
光分路器设置位置在光交接箱时，ODN支线含有用户接入层光缆的（ ）___
A. 主干光缆
B. 配线光缆
C. 中继光缆
D. 汇聚光缆
E.
【单选题】
OLT 上PON口下行输出光功率为2.8dBm，在用户侧测得下行光功率为-19.8dBm，则该光路上的实际损耗为()___
A. 17dB
B. 17dBm
C. 22.6dB
D. 22.6dBm
E.
【单选题】
（ ）的作用是为光接入网提供网络侧与本地交换机之间的接口，并经一个或多个ODN与用户侧的ONU通信___
A. OLT
B. ODN
C. ONU
D. ONT
E.
【单选题】
（ ）为OLT与ONU之间提供光传输手段，其主要功能是完成光信号功率的分配任务。 ___
A. OLT
B. ODN
C. ONU
D. ONT
E.
【单选题】
FBT类型规格为1:2的分路器插入损耗小于或等于（）dB___
A. 1.8
B. 3.6
C. 7.3
D. 10.7
E.
【单选题】
PLC类型规格为1:8的分路器插入损耗小于或等于（ ）DB。___
A. 1.8
B. 3.6
C. 7.3
D. 10.7
E.
【单选题】
1:16分路器插入损耗典型值(均匀分光，不含连接器损耗)为（ ）dB___
A. ≤3.6
B. ≤7.3
C. ≤10.7
D. ≤14.0
E.
【单选题】
1:32光分路器的损耗最大不超过（ ）dB___
A. 14
B. 15
C. 17.4
D. 18
E.
【单选题】
1:64的光分器，光功率损耗约为（ ）dB___
A. 18
B. 16
C. 20
D. 25
E.
【单选题】
EPON R/S-S/R点衰耗范围：ONU发射光功率0dBm~4dBm，接收光灵敏度为（）___
A. -24dBm
B. -25dBm
C. -26dBm
D. -27dBm
E.
【单选题】
EPON接口的有效带宽约为（ ）M。___
A. 1.25
B. 960
C. 1024
D. 1250
E.
【单选题】
EPON提供的各种业务中，优先级最高的是（）___
A. 语音
B. 视频
C. 宽带
D. 以上优先级相等
E.
【单选题】
EPON为点对多点系统，为保证上行数据有效传输，系统采用了以下哪种技术（）___
A. FDM
B. WDM
C. TDMA
D. CDMA
E.
【单选题】
EPON系统中支持最大的传输距离为（ ）公里。___
A. 10
B. 15
C. 20
D. 60
E.
【单选题】
EPON下行采用广播方式，ONU接收数据时，仅接收符合自己的（ ）的帧或者广播帧。___
A. MAC
B. SN
C. LLID
D. IP地址
E.
【单选题】
FTTH ODN网络拓扑结构一般属于下列( )类型。 ___
A. 树形
B. 星形
C. 总线
D. 环形
E.
【单选题】
GPON技术可以承载哪些业务（ ）___
A. ATM
B. TDM
C. Ethernet
D. 以上都可以
E.
【单选题】
GPON将业务带宽分配方式分为4种类型，优先级从高到低分别是（ ）。___
A. 保证带宽、固定带宽、非保证带宽和尽力而为带宽
B. 保证带宽、非保证带宽、固定带宽和尽力而为带宽
C. 固定带宽、保证带宽、尽力而为带宽和非保证带宽
D. 固定带宽、保证带宽、非保证带宽和尽力而为带宽
E.
【单选题】
GPON系统采用的最大分光比为（ ）___
A. 1：16
B. 1：32
C. 1：64
D. 1：128
E.
【单选题】
OLT和ONU之间的动态分配协议是（）___
A. SBA
B. OBD
C. DBA
D. CBA
E.
【单选题】
OLT设备的PON口发射光波长是（ ）。___
A. 1310nm
B. 1490nm
C. 990nm
D. 1530nm
E.
【单选题】
ONU的作用是为光接入网提供直接的或远端的( )接口。___
A. 计算机
B. 局端
C. 用户侧
D. 互联网
E.
【单选题】
ONU设备和软交换控制设备之间控制协议采用的传输类型是（ ）。___
A. SCTP
B. TCP
C. UDP
D. RTP
E.
【单选题】
PON的无源特性主要体现在哪个位置（ ）。___
A. OLT
B. POS
C. ODN
D. ONU
E.
【单选题】
PON的组成不包括（ ）。___
A. 光中继器,位于ONU和OLT之间,放大光信号, 扩大光网络覆盖范围
B. 光线路终端(OLT),在光接入网（OAN)的网络端提供至少一个网络业务接口
C. 光网络单元（ONU)提供通往ODN的光接口,用于实现OAN的用户接入
D. 光配线网（ODN)位于ONU和OLT之间,ODN具有无源分配功能
E.
【单选题】
PON的组网方式中，（ ）是最终的理想组网方式。___
A. FTTH
B. FTTB
C. FTTC
D. FTTN
E.
【单选题】
PON的组网模式为（ ） 。___
A. 点到点
B. 点到多点
C. 多点到多点
D. 多点到点
E.
【单选题】
PON数据业务中ONU上行波长是（ ）。___
A. 1310nm
B. 1270nm
C. 1490nm
D. 1550nm
E.
【单选题】
PON系统采用（ ）技术,实现单纤双向传输。___
A. TDM
B. WDM
C. CDMA
D. FDM
E.
【单选题】
PON系统采用单纤双向技术，上下行信号采用信号波长为（ ）___
A. 上行1490nm/下行1310nm
B. 上行1310nm/下行1490nm
C. 上行1550nm/下行1310nm
D. 上行1310nm/下行1550nm
E.
【单选题】
PON系统通过（ ）实现一点对多点网络结构。___
A. OLT
B. POS
C. 光交箱
D. 光纤分纤箱
E.
【单选题】
PON系统中，在OLT与ONU之间分光器级联一般不超过（ ）级。___
【单选题】
PON系统中ONU向OLT发送的数据采用( )技术。___
A. 广播
B. TDM
C. FDM
D. TDMA
E.
