—How was your day off yesterday?—Perfect! It was my grandma’s birthday. We had a big cake

问题补充：

—How was your day off yesterday?

—Perfect! It was my grandma’s birthday. We had a big cake.

A. eighty B. eightieth C. the eightieth

答案：

解析：考查数词的用法。表示“某人多大生日”应该使用序数词，且不需要使用定冠词。