Everyone is supposed ________ a seat belt in the car．

A．wearing

B．to wear

C．to be worn

Look!They ________ their classroom．

A．clean

B．are cleaning

C．cleaned

D．was cleaning

My sister ________ for three years before she went to college．

A．had worked

B．worked

C．has worked

D．have worked

He said that he ________ never ________ such a beautiful picture before．

A．has…seen

B．had…seen

C．have…seen

D．was…seeing

By the time Dave got up, his mother ________ breakfast．

A．has cooked

B．had cooked

C．cooked

D．have cooked

They ________ 100,000 trees by the end of 1994．

A．planted

B．has planted

C．have planted

D．had planted

My uncle ________ since he left school．

A．smoked

B．was smoking

C．has smoked

D．had smoked

Lucy and Lily ________ in Beijing for nearly two years．

A．are

B．were

C．will be

D．have been

My father has lived here ________．

A．for three years

B．since three years

C．for three years ago

D．three years ago

They got here ________．

A．a moment ago

B．for a moment

C．since a moment ago

D．sometimes