----How about the pollution in the countryside?
--- Luckily, it's not as serious as _______ in the big cities.
A. that B. it C. one D. Those
---Someone is knocking at the door. Who may it be?
---It ______ be Tom. He is still in the school.
A. can’t B. mustn’t
C. couldn’t D. may not
Lucy had few close friends. So she didn’t know ________ about the trouble.
A. who to talk B. who to talk to
C. who to say D. what to talk
Her singing lessons her five hours a week．
A．take B．spend C．cost D．Pay
He can’t state clearly how long he has ___________ the bicycle?
A. keep B. buy C. bought D. Had
----How can I improve(提高) my listening skills?
-----_______________more.
A. Listen B. Listening
C. To listen D. By listening
