Butterflies ______ a sweet liquid produced by flowers, which bees and other insects collect.

I haven’t been home to see my parents for two weeks; I _______ them.

—How did the fire_____?--By a car accident.

   the buildings were knocked down in the earthquake in the city of  Tangshan..

Doubting that the traveler carried drugs, the Customs officer stopped him and _______ his suitcase, but found nothing at all.