Sentence Correction

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

OA is E

I have two questions about this SC.

-When I say 'costly irrigation & application of commercial fertilizer' is costly modifying both irrigation and commercial fert ?

- In D if we change " ... was required..." to " ...were required..." would both D and E mean the same thing?

-When I say 'costly irrigation & application of commercial fertilizer' is costly modifying both irrigation and commercial fert ? Yes

- In D if we change " ... was required..." to " ...were required..." would both D and E mean the same thing? No, application modifies irrigation. Application of irrigation doesn't make sense