---what shall we do tonight then?

---              whatever you want.

Help yourself

No problem

It's a deal

It's up to you

考查交际用语。句意：---我们今晚做什么。---由你决定，你想干什么都行。根据空格后的 whatever you want，以及句意可知空格处填It's up to you由你定。故选D项。

According to Professor Johnson, we don't have to read the book if we don't want to, as it is              .

worthwhile

necessary

optional

serious

考查形容词词义辨析。句意：根据约翰逊教授的说法，如果我们不想读这本书，就不必读，因为它是可选择的。A. worthwhile值得的； B. necessary 必要的；C. optional 可选择的；D. serious 严肃的，认真的。根据“  we don't have to read the book if we don't want to”可知，这本书读不读都可以，由此可知它是“可选择的”。故选C项。

It has been warned that        to the surroundings with people infected by Covid-19 without any

protection can lead to severe result.

being exposed

exposed

having exposed

to expose

考查非谓语动词。句意：有人警告称，在没有任何保护措施的情况下，暴露在有感染 Covid-19的人环境中会导致严重的结果。分析句子结构可知expose在句中应用非谓语动词形式，表示“暴露”短语为be exposed to,且从句中缺少主语，expose 与主语people是被动关系，故应用动名词的被动式作主语。故选A项。

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。

If you don't understand something, you may resrarch, study, and talk to other people          you figure it out.

because

though

until

since

考查连词。句意：如果遇到不懂的东西，你可以搜索、研究，和别人交流直到弄明白。A. 因为； B. 尽管；C.until直到；D.since自从，因为。根据句意可知，until符合语境。故选C项。