He has proved -----for the job,and we are afraid that he'll have to leave this company.AinsufficientB unable Cdeficient

He has proved -----for the job,and we are afraid that he'll have to leave this company.
AinsufficientB unable Cdeficient

A,与for搭配, 对什么不足

B
deficient 形容词 缺乏的;缺少的;不足的
insufficien不够的, 不足的, 不充分的; 不适当的; 缺乏体力、能力或技巧的; 不胜任的 be insufficient to
be unable for...无法为...