I didn't know what to say ________, then an idea occurred ________ me．

A.at a time; to

B.for a time; to

C.for a time;/

D.at one time; for

答案及解析： B

本题考查了由time构成的词组，根据归纳，A、D两项均不合题意，for a time意为“一度”，occur与happen同义，接宾语需加介词to，答案为B．