These young trees must .A. look after wellB. be look after wellC. be looked well　D. be loo

问题补充：

These young trees must .

A. look after well

B. be look after well

C. be looked well

D. be looked after well

答案：

A. look after well

B. be look after well

C. be looked well

(答案→)D. be looked after well

解析：句意：这些树必须被很好的照顾。look after照顾。主语trees与动词look after之间是被动关系。因此用被动形式be looked after。故选D。