-How was your weekend? ---Great! It was my grandfather’s birthday. We enjoyed ourselve

问题补充：

---How was your weekend?

---Great! It was my grandfather’s birthday. We enjoyed ourselves.

A. seventy

B. seventieth

C. the seventieth

D. seventeenth[

答案：

A. seventy

(答案→)B. seventieth

C. the seventieth

D. seventeenth[

解析：句意:--你的周末过得怎样？--很好，那是我祖父七十岁的生日，我们玩得很高兴。这里指的是祖父的第七十个生日，应该用序数词，当序数词前有形容词性物主代词时，序数词前就不能再用定冠词。根据句意故选B。