根据汉语意思完成句子，每空一词。

1．我以前经常梦见坐火车，梦见去首都。  

     I often _____ _____ the train,about going to the capital.

2．不要忘记你是哪里人。  

     Don't forget where you_____ _____.

3．现在火车就在我前面，马上就要开车了。  

     Now the train is in front of me, to _____ _____ soon.

4．我的母亲点点头，说不出话来。  

     My mother nodded, unable _____ _____

5．我跳上火车后，发现到处都是人和包。  

     After I _____ _____ the train, I found there were people and bags everywhere.

6．请大声回答这个问题。  

     Please answer the question _____ _____ _____ ______.

临床试验设计的基本原则是

A．随机

B．对照

C．重复

D．多中心

E．以上全是