The flu is believed       by viruses that like to reproduce in the cells inside the human nose and throat.

Our teachers often tell us, “the harder you study, the more questions you will think of_____．”

---How do you like your new assistant?
---To tell you the truth,I've found the girl _____.

I kept on _______to her until the train disappeared completely in the darkness.

The documents are very important, so they are supposed ______ as soon as possible.

With the guide _______ the way, we finally got to the beautifu mountain village which we
were looking for.

The plan has to be _______ to meet the real situation.

_______ your answers with those at the back of the book to see if they are right.

To his disappointment,the opinion he had stuck _____out wrong.

Beijing has a population of 17 million, ________ it one of the largest cities in China.