他缺乏自信，总是怀疑自己能否胜任这份工作。

He lacks ___self-confidence and always doubts whether he can handle the job.

她的自信让她在面试中表现出色。

Her ___self-confidence helped her excel in the interview.

公开演讲帮助她增强了自信心。

Public speaking helped her develop ___self-confidence.