The monument was built in honor of the explorer who was believed _____ the river.

A. to have discovered    　　　　　　　 B. to have been discovered 

C. to discover     　　　　　    　　　 D. having been discovered

Paper produced every year is　　　　 the world’s production of vehicles(车辆).

A.three times weight of　　　　　　　　　 B.three times the weight of

C.as three times as heavy　　　　　　　　 D.three times so heavy as

He must have finished the work by the end of last month, _______he?

A. mustn’t　　 B. hadn’t　 C. didn’t　 D. hasn’t

The children ＿＿very quiet；I wonder what they ＿＿up to.
A. were； are being    B. are being；are     C. are；do        D. are being；do

Many stars in the universe are 　　　　 (看不见的) to our eyes.?

The medicine works more effectively_____you drink some hot water after taking it.
A. as    B. until    C. although     D. if

They were forced to leave their homeland _____ the Nazis got there and killed many people.

A. that　　　　 B. since　　　 C. because　 D. because of

We are always warned not to act ____ what will happen afterwards.

A. in the event of　 B. as a result of　　 C. regardless of D. in spite of

It is engineers that have 　　　 the distant countryside by radio or telephone.

　 A. linked up　　 　　　　 B. connected to C. linked to　　 D. connected with