问题
选择题
— What are the _______ doing there?
— They are busy _______ their science experiment.
A．Boys students; to do
B．Boy students; to do
C．Boys students; doing
D．Boy students; doing
答案
答案：D
考查名词复数和非谓语动词的用法。男学生的复数表示为boy students，固定结构“be busy doing sth”忙于做某事。