Incredulous /ɪnˈkredʒ.ə.ləs/ adj. 的;不能相信的;表示怀疑的
Meaning: not wanting or not able to believe something, and usually showing this
1) 前缀:in- 否定
2) 词根:cred- 相信(credit card 信用卡)
3) 后缀:-ulous 形容词后缀
e.g. She listened to his explanation with an incredulous smile. 她带着难以置信的微笑听完了他的解释。