This is certainly the case, but ____ it is a mistake or not I don’t know.
A. if B. even though C. whether D. that
This is certainly the case, but ____ it is a mistake or not I don’t know.
A. if B. even though C. whether D. that
C
引导宾语从句时,whether 和if常可互换,但如从句提前,则只能用whether。