We _______ on it for several hours but we have not yet reached any conclusion.

A．work B．are working     C．have been working D．have been worked

Great changes ______ in my hometown in the past twenty years.

A. took place  B. have taken place C. were taken place       D. have been taken place

He has changed a lot. He _________ not what he _________.

A. is, is   B. was, was    C. is, was       D. was, is

The mother believes that John's stupid, but it's different _____ of Mary; she's just lazy.

A. in spite B. in the case C. in the course D. in case

It is no longer a problem _______ the poor children in this district can go to school.

      A. that           B. whether        C. so            D. because

Many workers were organized to clear away        remained of the World Trade Center.

A. those      B. that         C. what       D. where

You cannot be ____ careful when you drive a car.

A. very B. so C. too D. enough

____ the essay a second time, the hidden meaning will become clearer to you.

   A. While reading   B. After reading     C. Your having read   D. When you read

Postage ______, the necklace will cost you at least 650 yuan.

   A. including B. included C. include D. to be included

From my point of view，the theory that           by the scientist is not quite scientific．

      A．was risen                    B．brought up

      C．had been raised            D．was put forward