Question

9. Sometimes new ideas have to be tested many times before         . (accept)

有些时候新的想法必须经过多次试验后才能被接受。

Answer 1

9. being fully accepted/they are fully accepted before既可用作介词，亦可用作连词，因此，此处既可用从句结构，亦可用分词短语，但都应为被动形式。