The flowersevery day or they’ll die.A. can be wateredB. should waterC. must be wateredD.

问题补充：

The flowersevery day, or they’ll die.

A. can be watered

B. should water

C. must be watered

D. water

答案：

A. can be watered

B. should water

(答案→)C. must be watered

D. water

解析：句意：这些花必须每天都浇水，不然会死去。句子要用被动语态，其结构为be+动词过去分词；如果前面有情态动词，be用原形；情态动词can能够；must必须；结合语境故选C。