来自question,问题。即有问题的，可疑的。

1. His best friend was killed by police under extremely questionable circumstances.

他最好的朋友在极其可疑的情况下被警察打死了。

2. It is questionable whether the expenditure on this project is really justified.

该项目的开支是否真的合理还未可知。

3. He has been dogged by allegations of questionable business practices.

他一直被那些指控他有不正当商业行为的说法所困扰。

4. It's questionable whether anything of substance has been achieved.

是否已经取得了任何实质性进展还是个问题。

5. The conclusions that they come to are highly questionable.

他们得出的结论大有问题。