OG 184 菜鸟总结中关于as

184. 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

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

最后的菜鸟总结中说

as表原因，没有逗号时表伴随。/ as放在句首一般会产生歧义

为什么会一般会产生歧义啊？？nn指教

as 在句首，可以作「因为....」，也可以作「当....」的意思。

thx 哈