这句句子的结构怎么理解？

The computer company’s present troubles are a result of technological stagnation,
        marketing missteps, and managerial blunders
        so that several attempts to revise corporate strategies have failed
            to correct it.

A.      so that several attempts to revise corporate strategies have
        failed to correct it.

B.       so that several attempts at revising corporate strategies have
        failed to correct.

C.      in that several attempts at revising corporate strategies have
        failed to correct them.

D.      that several attempts to revise corporate strategies have
        failed to correct.

E.       that several attempts at revising corporate strategies have
        failed to correct them.

D