(2013·威海两校模拟)________ the earth to be flat, many feared that Columbus would fall off the edge of the earth.

_____ with out girls, she is more active in class.

.At this moment the bell rang _______ the end of class.　

When he came back, he found the bag he had ______________ over the seat was gone.

In the past month, cruel snowstorms hit some European countries and America ,    great transportation problems in these countries.