og128没有问过的问题，请nn指教

128. New hardy varieties of rice show promise of producing high yields without the costly requirements of
irrigation and application of commercial fertilizer by earlier high-yielding varieties.
(A) requirements of irrigation and application of commercial fertilizer by earlier high-yielding varieties
(B) requirements by earlier high-yielding varieties of application of commercial fertilizer and irrigation
        
(C) requirements for application of commercial fertilizer and irrigation of earlier high-yielding varieties
(D) application of commercial fertilizer and irrigation that was required by earlier high-yielding varieties
(E) irrigation and application of commercial fertilizer that were required by earlier high-yielding varieties

Answer to Question 128
Choice E, the best answer, clearly and grammatically expresses the idea that two costly procedures, irrigation
and the application of... fertilizer, were required by earlier high-yielding varieties of rice. In A, the placement
of by earlier... varieties immediately after application of fertilizer suggests that the varieties applied the
fertilizer. In B and D, the phrase application of... fertilizer and irrigation is ambiguous in meaning: it cannot be
clearly determined whether applying fertilizer and irrigating are a single operation or two distinct operations. In C,
only irrigation--not both irrigation and fertilization--is clearly associated with the earlier... varieties of rice.

我的问题是，为什么B会产生ambiguity呢？前面不是有requirements吗？虽然我知道B不如E好，但是requirements不足以消除它的ambiguity吗？请高手看看

还是谢谢你，哈

requirements by earlier high-yielding varieties of application of commercial fertilizer and irrigation
    

我知道你的意思了，现回答如下：

requirements by （earlier high-yielding varieties of application of commercial fertilizer） and irrigation

requirements by earlier high-yielding varieties of application of commercial fertilizer and irrigation
    

这样会有歧义了吧？