How to distinguish when to use “Fewer” and when to use “Less”
In 1979 lack of rain reduced India’s rice production to about 41 million tons, nearly
25 percent less than those of the 1978 harvest.
(A) less than those of the 1978 harvest
(B) less than the 1978 harvest
(C) less than 1978
(D) fewer than 1978
(E) fewer than that of India’s 1978 harvest
Source: OG 2016 – Question 12 from Sentence Correction.
By elimination we can narrow down to option (C) and option (E)
Can you please help how to decide when to choose “Fewer” and when to choose “Less” based on grammatical rules