We were doubtful about the practicability of the plan.

我们怀疑这个计划是否切实可行。

《牛津词典》

None of them has the same responsibilities. None has the nation holding its breath every time doubtful information about their match fitness comes up.

并不是每个人都有相同的责任，也不是每个人每次都需要整个国家屏住呼吸来等待其能健康上场比赛的消息。

youdao

They are able to get you into negative state of mind very quickly, therefore you may become doubtful about wanting to change.

他们能很快把你拉到消极的国度里面，从而你可能开始怀疑，是否想要改变。

youdao

One clear danger is that they may alienate customers, who will welcome better service but may be more doubtful about uses of the technology such as finely segmenting the market or targeting customers individually.

ECONOMIST: Always-on people

He was doubtful about the ability of the army to cope with conditions in a land they had no knowledge of.

ECONOMIST: Cyrus Vance

Doubtful about the accuracy of Mr. Hornsby's data, Mr. Berger checked it against the NFL data set and found Pro Football Focus was nearly perfect.

WSJ: In Super Bowl, Giants Go Long for a Number Cruncher