Tom had made up his mind to give it up but on second thought he determined to have thir

问题补充：

Tom had made up his mind to give it up, but on second thought he determined to have third try.

A. a ; a

B. 不填 ; a

C. 不填; 不填

D. the ; a

答案：

A. a ; a

(答案→)B. 不填 ; a

C. 不填; 不填

D. the ; a

解析：本题考查冠词。on second thought固定结构，转念一想;a third time,又/再一次，无论序数词是几，都加a/an，句意：约翰本来打定主意放弃了，但转念一想，又决定再试一次。