Sentence Correction

Laboratory rats and mice live up to 40 percent longer than usual when fed a diet of at least 30 percent fewer calories than that which they would normally eat, but that otherwise contains all necessary vitamins and nutrients.

a. of at least 30 percent fewer calories than that which they would normally eat, but that otherwise
b. with at least 30 percent fewer calories than what they would normally eat though otherwise it
c. that has at least 30 percent fewer of the calories that they would normally eat, but otherwise it
d. that has at least 30 percent fewer calories than they would normally eat but that otherwise
e. that has at least 30 percent fewer calories than that which they would normally eat, though that otherwise

May I request experts to explain the official explanation of incorrect answers A and E of this question?


A)The sentence awkwardly describes a diet of calories;
the singular pronoun that logically refers to diet but syntactically is compared with the plural calories.

I understand the first part but i am not able to understand the part "singular pronoun "that" is syntactically compared with the plural calories". My question is how?


E)The singular relative pronoun that nonsensically refers to the plural calories,and the second appearance of that is without a referent.

In this explanation also the part where it says "The singular relative pronoun that nonsensically refers to the plural calories". As far as i understand that relative pronoun may refer to plural nouns. if my understanding is correct then why in the explanation above "that" is defined as singular relative pronoun.

I would also like to understand what exactly is hidden/omitted in the right choice (option D) after fewer calories than

Is it calories

Laboratory rats and mice live up to 40 percent longer than usual when fed a diet that has at least 30 percent fewer calories than (calories) they would normally eat but that otherwise contains all necessary vitamins and nutrients.

OR

the diet

Laboratory rats and mice live up to 40 percent longer than usual when fed a diet that has at least 30 percent fewer calories than (the diet) they would normally eat but that otherwise contains all necessary vitamins and nutrients.

OR is it something else? Kindly explain.

When used as a MODIFIER, that may refer to a singular or plural antecedent:
CORRECT: the book that John wrote
CORRECT: the books that John wrote

When used as a COPY PRONOUN in a comparison:
that must serve to refer to a SINGULAR antecedent.
those must serve to refer to a PLURAL antecedent.

A)The sentence awkwardly describes a diet of calories;
the singular pronoun that logically refers to diet but syntactically is compared with the plural calories.

I understand the first part but i am not able to understand the part "singular pronoun "that" is syntactically compared with the plural calories". My question is how?

A: of 30 percent fewer calories than that
Here, that seems refer to diet, the nearest preceding singular noun.
Conveyed meaning:
of 30 percent fewer calories than the diet
Here, calories are illogically compared to the diet.
Eliminate A.

E)The singular relative pronoun that nonsensically refers to the plural calories,and the second appearance of that is without a referent.

In this explanation also the part where it says "The singular relative pronoun that nonsensically refers to the plural calories". As far as i understand that relative pronoun may refer to plural nouns. if my understanding is correct then why in the explanation above "that" is defined as singular relative pronoun.

When used as a copy pronoun in a comparison, that must serve to refer to a singular antecedent.

I would also like to understand what exactly is hidden/omitted in the right choice (option D) after fewer calories than

Is it calories

Laboratory rats and mice live up to 40 percent longer than usual when fed a diet that has at least 30 percent fewer calories than (calories) they would normally eat but that otherwise contains all necessary vitamins and nutrients.

OR

the diet

Laboratory rats and mice live up to 40 percent longer than usual when fed a diet that has at least 30 percent fewer calories than (the diet) they would normally eat but that otherwise contains all necessary vitamins and nutrients.

OR is it something else? Kindly explain.

Check my second post here:
https://www.beatthegmat.com/lab-rats-que ... 89-15.html