问题

I was about to give up my effort to solve a problem __________ a good idea struck me
A:when
B:while
C:until
D:before
B:while
C:until
D:before
正确答案是:
同类题型
_____there are many different typesof food, some animals spend their lives eating only one type.
Our city has experienced _______ this year as it did last year.
Mother was in the kitchen ______ lunch while I was ______ the coming exam.
is the library from our school—It’s quite near. Just three miles .