Question

When you are planting trees, the trees ________ straight in the hole.

A．must put

B．must be put

C．a(chǎn)re putting

D．is put

Answer 1

B

試題分析：句意為：植樹的時候，樹必須直立放到坑里。根據(jù)語境，句子的主語是“the trees”，是動作的承受者，應(yīng)用被動語態(tài)。故選B。