—Why does the lake smell terrible?
—Because large quantities of water ________.
A．have polluted B．is being polluted
C．has been polluted D．have been polluted
His sister left home in 1998，and ________ since.
A．had not been heard of B．has not been heard of
C．had not heard of D．has not heard of
In the near future，more advances in the robot technology ________ by scientists.(2011·湖南)
A．are making B．are made
C．will make D．will be made
John, a friend of mine, who got married only last week, spent $3,000 more than he ________ for the wedding.
A．will plan B．has planned
C．would plan D．had planned
—Hurry up！Alice and Sue are waiting for you at the school gate.
—Oh！I thought they ________ without me.
A．went B．are going
C．have gone D．had gone
We arrived at work in the morning and found that somebody ________ into the office during the night.(2011·江西)
A．broke B．had broken
C．has broken D．was breaking
