一、单选题(总题数:10,分数:10.0分)
1、Last month four engineers ___________to help solve the technical problems.
  A、have sent
  B、sent
  C、were sent
  D、had sent
答案: C
解析:
根据句中的时间状语Last month(上个月)可知，本句应用一般过去时，表示在过去某一段时间内发生的动作。根据句意可知，four engineers和send(派遣)之间是逻辑上的动宾关系，所以应用一般过去时的被动语态，即谓语动词用“was/were+过去分词”的形式。故选C。
2、2By the time you get to the office, I ______all the documents for the meeting.
  A、prepared
  B、was prepared
  C、was preparing
  D、will have prepared
答案: D
解析:
by the time意为“到……的时候(为止)”,可以用来引导时间状语从句，如果从句使用了一般现在时(表示将来),那么主句常用将来完成时，表示“截止到从句动作(表示 ……此处隐藏37841个字…… r />①流行病epidemic
②新型冠状病毒肺炎COVID-19
③医护人员medical workers


答案:Dear medical workers,
I'm a student from Peking University. I am writing to express my sincere gratitude to you all foryour selfless devotion.
As COVID-19 spreads throughout the country, many people suffer from it. It is your actions thatsave many lives. Many of you work day and night to guard our safety but never ask for reward. You arethe most selfless people in the world. In my view, you set a good example to the world announcingthat China never gives up!
Thanks again for what you have done for us. I'm firmly convinced that we will conquer theepidemic by our joint efforts.
Yours sincerely,
Li Ming