◆idyllic adj. 田园诗的(like a description of the country life in a poem)

Eg: He is leading an idyllic life. 他过着田园诗般的生活。

◆dubious adj. 可疑的，怀疑的(not certain and slightly suspicious about sth; doubtful)

联想：

dubious

be dubious about/of  对...怀疑,对...不肯定，主要表示不肯定的，不确定的

Eg: I am dubious about her motives. 我怀疑她的动机。新概念英语怎么样

suspicious / doubtful：suspicious语气比doubtful肯定

Eg: It's very suspicious that she was in the house when the crime happened.

I am not sure about your ability to do so. 或者：I am doubtful of your ability.

我们可以看看这两个词对应的动词：doubt / suspect

Eg: I suspect that he stole the car last night. 语气较肯定的猜疑

I doubt whether he stole the car. 语气不太肯定

questionable强调质疑，有问题的，值得争议的

This is a questionable conclusion / decision.

skeptical 怀疑论的，怀疑的 (与suspicious意思接近，但属于正式用法)

Eg: Your idea is skeptical.