In the era of market economy, the concept of “Consumer First” should be ___by manufacturers.( )

A. who send

B. being sent

C. sending

D. having sent

A. used to read B. am used to reading

C. use to read D. have used to read

A. had seen

B. had been seeing

C. have seen

D. have been seeing

A.what

B.which

C.that

D.who

A.unless, don’t study

B.unless, study

C.if, study

D.if, not study

A. didn’t he

B. wouldn’t you

C. hadn’t he

D. don’t you

A. didn’t say

B. wouldn’t say

C. hadn’t said

D. don’t say

A. am going to

B. will

C. would

D. was going to

A. lose

B. lost

C. would lose

D. will be

A. although

B. nevertheless (然而、不过)

C. unless

D. Once (一旦)