新政策的成功与否仍不确定。

The success of the new policy is still ___be ___in ___doubt.

如果你对答案不确定，就向老师请教。

If you are ___be ___in ___doubt about the answer, ask your teacher for clarification.

他的资格一度受到质疑，直到他出示了必要的证书。

His qualifications were ___be ___in ___doubt until he produced the necessary certificates.