dubious 

/?d?u?.bi.?s/

thought not to be completely true or not able to be trusted

半信半疑的，可疑的;不確定的;不可信的

These claims are dubious and not scientifically proven.

這些說法未經科學證實，有些可疑。

She knew he really wanted to help her; however, she was dubious about his ability to help.

她知道他是真心想幫她，但對他有沒有那種能力卻半信半疑。

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