I was doubtful about what they have said, but I didn't say anything.

我对他们说的话感到很怀疑，但我也没说什么。

youdao

It is doubtful whether an investor's sniping at management can ever be anything other than counterproductive, but in this case it is clearly not justified.

投资者对管理层的攻击是否只会适得其反是值得怀疑的，但在这种情况下，这显然是不合理的。

youdao

As soon as he finished, his supporters applauded vigorously, but most of the masses were taken aback and exchanged doubtful glances.

他的话完了，他的几个支持者拼命地鼓掌，而更多的人却噤若寒蝉，面面相觑。

《新英汉大辞典》

But some are doubtful the reforms will work. Boston University School of Law professor Cornelius Hurley.

VOA: standard.2010.03.16

State Department Spokesman P.J.Crowley said the United States welcomes the visit by President Lula, but that it is doubtful it will yield anything useful.

VOA: standard.2010.05.14

Thus customers with good credit quality are actively courted by multiple banks, but more doubtful loan applicants are shunned.

FORBES: Credit Availability Forecast: 2012-2014

UN's arrival, but remained doubtful of their enemies' desire for peace.

ECONOMIST: Eritrea

All our skaters will remain at the training camps and be competition-ready in case, but I am doubtful.

BBC: Tokyo cancels World Figure Skating Championships