Air pollution, together with littering, __________ many problems in our large industrial cities today．

A．causes

B．cause

C．caused

D．causing

His advice made me happy, but __________ others angry．

A．making

B．to make

C．/

D．make

__________ the flight to Beijing will be delayed is __________ I’m especially worried about．

A．If; what

B．Whether; that

C．When; that

D．Whether; what

The split between humans and living apes is thought by some scholars __________ 15 to 20 million years ago．

A．to occur

B．occurring

C．to have occurred

D．having occurred

David applied for the position three times __________ he finally got it．

A．until

B．when

C．before

D．after

Many questions have been answered by John．He must have previewed the lessons last night, __________ he?

Look, __________ fashionable clothes is she wearing that all the eyes are fixed on her!

A．so

B．such

C．how

D．what

Sue __________ come together with us tonight, but she isn’t very sure yet．

A．must

B．may

C．need

D．will

Parents should tell their children __________．

A．what they should behave

B．what should they behave

C．how they should behave

D．how should they behave

There is little doubt __________ her advice is of greater value to us．

A．that

B．whether

C．why

D．if