Jack was born five years ago and this is his birthday.A. fifthB. fiveC. Fifteen

问题补充：

Jack was born five years ago and this is his birthday.

A. fifthB. fiveC. Fifteen

答案：

解析：句意：杰克是五年前出生的，这是他的第五个生日。根据句意应该用序数词表示第五个；故选A。