12. We need to get to the root of the problem______ we can solve it.
A
while
B
after
C
before
D
as
while当……时；after在……之后；before在……之前；as由于。故选项C符合答案。
根据句意在解决问题之前，我们需要先找到根源。
常见连词用法记忆不准致错。