Everyone knows Olympic Games will be held in London in July .A. the 30th B. the 30C.

问题补充：

Everyone knows Olympic Games will be held in London in July, .

A. the 30th

B. the 30

C. 30

D. a 30

答案：

(答案→)A. the 30th

B. the 30

C. 30

D. a 30

解析：句意:每个人都知道第三十届奥运会七月将要在伦敦举行.结合语境可知本句中是用序数词表示顺序,作定语,故选A.