1·I'm doubtful of what he said.
怀疑他所说的话。
2·He was doubtful of the patient's recovery.
他怀疑病人是否痊愈。
3·When the masses are doubtful of those above, the state is unstable.
民众都对上级怀有疑虑，国家就不会安定。
4·Most netizens were doubtful of the necessity of this costly public washroom.
大多数网民质疑有没有必要设立这么昂贵的公厕。
5·And if you do take one, you'll probably make the shop assistants feel unease, they might be doubtful of your intentions.
倘若你自己带着拎包进店，反倒会使店家觉得不踏实，没准会怀疑你是扒手呢！
6·We succeed in winning the contract, but for a long time we were sailing against the wind, and were doubtful of our success.
我们成功地赢得了合约，但长时间里我们在困难中工作，并对我们是否能成功曾持怀疑态度。
7·I was doubtful of the merits of such restrictions, but then this may have been the only way to cut off the power demand for money.
我当时对他的约束办法有怀疑，但也认为可能是斩断权力借贷的唯一办法。
8·Ecologists argue that the benefits of treating sewage with disinfectants are doubtful.
生态学家们认为用消毒剂处理污水的好处是值得怀疑的。
—— 《柯林斯英汉双解大词典》
9·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》
10·When he weeded out "the most doubtful measures of aggression", only 28% supported a connection.
当他排除“最可疑的攻击手段”时，只有28%的人支持这种联系。