When it comes to modern communication, network safety is always a major          . 

concern

advantage

opportunity

solution

考查名词辨析。句意：当涉及现代通信，网络安全一直是一个主要令人担忧的问题。A. concern关心，令人担忧的事实或情况；B. advantage 优势；C. opportunity 机会；D.solution解决方案。网络安全一直是现代通信的个主要令人担忧的问题。故选A项。

It is well-known that crack cocaine is a powerful             drug and users become           to it much more easily if they smoke it.

addicted; addict

addictive; addict

addicted; addictive

addictive; addicted

考查形容词辨析。众所周知可卡因是一种强大的令人上瘾的毒品，如果使用者吸了它更容易上瘾得多。addicted上瘾的，着迷的；addict"shi使沉迷；使上瘾”是动词；addictive “使成瘾的，令人沉迷的”。第一空表示“令人上瘾的”用addictive，故排除A，C项；become addicted to “对....上瘾”，第二空填addicted。故选D项。

Don’t mention that at the beginning of the story, or it may             the  shocking end.

give out

give away

give up

give off

考查动词短语辨析。句意：不要在故事的开头提到它，否则会泄露令人震惊的结局。A. give out分发；B. give away泄露；C.give up 放弃；D. give off发出（光），根据“the shocking end”可知，此处表示“泄露”。故选B项。

All we need          a piece of advice on how we can improve our time management.

are

is

were

was

考查be动词和时态。句意：我们需要的只是一条关于如何改进时间管理的建议。分析句子可知，说明一般情况应该用一般现在时，这句话的主语是All we need, 所以为主语从句，当主语从句作主语时，谓语动词用单数，所以用is。故选B项。

It was along the Mississippi River _________ Mark Twain spent much of his childhood.

how

which

that

where

此处构成It was...that...强调句式，句中强调了介词短语along the Mississippi River。故选C。

The wise parents can tell whether their children are telling the truth         they listen to their excuses to wrong deeds.

the first time

every time

for the first time

for every time

考查时间状语从句。句意：每次听孩子对错误行为的辩解，聪明的父母都能分辨出他们是否在说真话。此处引导时间状语从句，表示“每一次” 应用every time。the first time表示“第一次”，与语境不符；for the first time作时间状语，不可引导从句；没有for every time 的表达方式。故选B项。

Tom wanted to play football with his friends in the street，but his father told him ________.

not to

not to do

not do it

do not to

考查动词不定式的省略。完整的形式应该是…，but his father told him not to play football with his friends in the street.为避免重复，常省去不定式动词，保留不定式符号to，故选A。

Tom looks so pale today. He ______ ill.

must be

had to be

should be

shall be

[翻译]汤姆看起来脸色不好，他一定生病了。[解析] A 试题解析：情态动词must表示推测。题目中表示肯定的推测。

The salesman scolded the girl caught         and let her off.

to have stolen

to be stealing

to steal

stealing

考查非谓语动词。句意：这个销售员责备了被抓住正在偷东西的女孩，然后，让她走了。分析句子结构，caught是过去分词作定语，修饰前面的名词 the girl,"女孩"和"偷东西"之间是主动关系，用现在分词作宾语补足语，构成catch sb doing sth结构。意为抓住某人正在做某事。故选D项。

He punished the children          their carelessness         making them pay for the damage.

by; for

with; by

for; by

about; with

考查介词。句意：他因为孩子们的粗心惩罚他们赔偿损失。根据句意可知：“their carelessness"表示他们被惩罚的原因，需用介词for表原因。"making them pay for the damage"表示他们被惩罚的方式，需用介词by表方式。故选C项。