【问】 At first I was of the opinion that you were decidedly right;_________ I am not sure.

A. on the second thought B. on second thought

C. on second thoughts D.on the second thoughts(《大学英语》1996年第3期)书上给的答案是C (on second thoughts)。难道不能选D(on second thougtht)吗?

【答】 on second thought也是正确的，主要用于美国英语，与on second thoughts同义。

I said I wouldn't do it，but on second thoughts(BrE)/on second thought(AmE)I think Iwill. (LDCE)

我本来说是不干的，但经过了再三考虑后，我想我还是干吧。

下面的托福题就没有让考生在on second thoughts与on second thought之间进行选择：

“Why didn't you go to his party last night，John?”

“_________，I changed my mind. ”

A. On a second thougtht B. By second thoughts

C. On second thoughts D. On the second thought(TOEFL，72. 3)