Some children were seen in the garden all the morning. It must have been who picked the flowers.
A. playing; they
B. to play; they
C. playing; them
D. play; them
网友回答
(答案→)A. playing; they
B. to play; they
C. playing; them
D. play; them
解析：考查非谓语动词与人称代词。句意：一些孩子被看到整个上午都在花园里玩。肯定是他们拔了这些花。现在分词做状语表示句子主语正在进行的伴随性动作。下文人称代词为从句的逻辑主语，故需用主格形式，选A。