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 of 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 earler high-yielding varieties

guys i am not looking for justification of right ans, i have a doubt on the usage of THAT....
what actually decides to what THAT refers is it the sub preceding THAT or the verb following THAT
as in this case the OA is E
but in the OA use of plural verb implies that the word THAT refers to a compound sub.....
however as per my understanding
X(sing) and Y(sing) that Verb(sing) as that refers to Y
pls i need to clear my concept on this one help me