—Listen! Is that Pingping playing the guitar?  —No. It __________be Pingping. He has gone to Beijing.

It was so dark outside that the little child ________ go out by himself. 

—Steve is good at writing short stories. — So he is. But he writes _______ than us. So he can’t get good grades in writing. 

Some aspects of a pilot's job      be boring, and pilots often      work at inconvenient hours．

Now that the sign reads, “No person ______ smoke here”, please choose a seat in the smoking area over there if you _______ smoke.