请教！

1.        As measured by the Commerce Department, corporate profits peaked in the fourth quarter of 1988 and have slipped since then, as many companies have been unable to pass on higher costs.

(A) and have slipped since then, as many companies have been unable to pass on higher costs

(B) and have slipped since then, the reason being because many companies have been unable to pass on higher costs

(C) and slipped since then, many companies being unable to pass on higher costs

(D) but, many companies unable to pass on higher costs, they have slipped since then（A）

(E) yet are slipping since then, because many companies were unable to pass on higher costs

这里的两个as充当什么成分阿。

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