It must have rained last night, ________ the ground is wet now.

A．for              B．because           C．since             D．now that

It was an unpleasant subject ____ we _____ for a long time.

A．about which…discussed                  B．about which…argued

C．over them…argued                     D．which…argued

Black clouds had completely ___ the sun.

A．blocked off        B．broken out        C．blocked out        D．broken off

How did you ___ to paint the whole house in a week?

A．try               B．manage           C．win              D．succeed

A heavy learning burden leads to unhealthy behaviors such as poor eating habits, which ___ damage the health of students.

A．in its turn         B．in return          C．in turn            D．by turns

Perseverance is a kind of quality --- and that’s ________ it takes to do anything well.

A．why              B．that              C．which            D．what

It is so wet there that the trees are extremely tall, some ________ over 90 metres.

A．are measured      B．measuring         C．measured         D．measure

An idea came to him ___ he might do the experiment in another way.

A．which            B．when             C．what             D．that