has already been pointed out only by correcting mistakes can you make progress.A. ItB. A

问题补充：

has already been pointed out, only by correcting mistakes can you make progress.

A. It

B. As

CThat

D. What

答案：

A. It

(答案→)B. As

C. That

D. What

解析：考查固定句型，固定句型As has already been pointed out意思“正如已经指出的那样”， It可以做形式主语或形式宾语；That只起引导作用，没有意义；What表示什么，可以引导从句，句子意思“正如已经指出的那样，只有通过纠正错误你才能进步”