He has proved his courage in the battle.
Through tests time and time again, this kind of rope strong.
A. was proved
B. has ben turned out
C. turned
D. proved
网友回答
A. was proved
B. has ben turned out
C. turned
(答案→)D. proved
解析：考查系动词用法。句意：通过一次次实验，结果证明这种绳子是结实的。turn out,prove作为证明是，结果是，原来是为系动词，无被动语态。