Rose was doubtful about the whole idea.

罗斯对整个设想持怀疑态度。

He was doubtful about accepting extra work.

他拿不定主意是否接受额外工作。

We were doubtful about the practicability of the plan.

我们怀疑这个计划是否切实可行。

I was still very doubtful about the chances for success.

我仍然不能肯定成功的可能性有多大。

I'm rather doubtful about his integrity.

我对这事的忠诚颇有怀疑。