—Will you join us in the game?—Thank you A. but why not?B. but I’d rather not.C. and I won

问题补充：

—Will you join us in the game?

—Thank you,

A. but why not?

B. but I’d rather not.

C. and I won’t.

D. and I’ll join.

答案：

A. but why not?

(答案→)B. but I’d rather not.

C. and I won’t.

D. and I’ll join.

解析：I’d rather not用于拒绝对方的邀请。根据所提供的情景Thank you可判断出不想参加比赛。why not意为“为什么不呢？”表示同意参加，与but矛盾。I won’t表示拒绝，不能与and连用。