As soon as she entered her own room she caught sight of the gift by her father.A. buying

问题补充：

As soon as she entered her own room, she caught sight of the gift by her father.

A. buying

B. bought

C. was bought

D. being bought

答案：

A. buying

(答案→)B. bought

C. was bought

D. being bought

解析：考查非谓语动词作后置定语。名词gift和动词buy之间是动宾关系，所以用过去分词作定语。选B。