UNESCO was established to encourage _______ among nations in the areas of education, science, culture, and communication.

A. When you are riding a motorcycle, wearing a helmet is not a must.

B. You needn't wear a helmet whenever you are riding a motorcycle.

C. Helmets must be worn at all times when you are riding a motorcycle.

D. If you are riding a motorcycle, you needn't wear a helmet.'

A. There are a lot of words in the dictionary for you to look at.

B. You can find the meaning of this word in the dictionary.

C. You should buy this dictionary to find the word you need.

D. The dictionary contains a lot of words except the one you need.

A. restricted

B. boosted

C. expanded

D. balanced

A. them

B. who

C. whom

D. whose

A. You shouldn't have lost your passport.

B. Your passport must be lost.

C. There must be a mistake in your passport.

D. You needn't have brought your passport.

A. under

B. into

C. off

D. for

A. wouldn't waste

B. hadn't wasted

C. hasn't wasted

D. didn't waste