Sentence Correction

I would like to raise a general question I seem to be having a problem with. I hope your analysis will be able to create a method to solve such question.

I have seen more than a few comparison question that tests the ability to make both sides logically comparable.
However it is not obvious how to use the comparison when action are involved. Can you tell me what is right and why:

My father works harder than your father.
My father works harder than your father does.

I feel the second one is better - comparing actions.

However, I have problem understanding the issue as it presented in the following question taken from the Verbal Review (q. 29):

A study commissioned by the Department of Agriculture showed that if calves exercise and associated with other calves, they will require less medication and gain weight quicker than do those raised in confinement.

(A) associated with other calves, they will require less medication and gain weight quicker than do
(B) associated with other calves, they require less medication and gain weight quicker than
(C) associate with other calves, they required less medication and will gain weight quicker than do
(D) associate with other calves, they have required less medication and will gain weight more quickly than do
(E) associate with other calves, they require less medication and gain weight more quickly than

OA: E

[spoiler]The books clearly states (in its usual clear explanation) that the "do" is "ungrammatically interrupts the comparison and should be eliminated"[/spoiler]

I hope we can find a clear way to distinguish the different options because this issue seems very common in the test. Thanks in advance,

A study commissioned by the Department of Agriculture showed that if calves exercise and associated with other calves, they will require less medication and gain weight quicker than do those raised in confinement.

(A) associated with other calves, they will require less medication and gain weight quicker than do
Exercise and associated is not parallel. eliminate

(B) associated with other calves, they require less medication and gain weight quicker than
Same as A

(C) associate with other calves, they required less medication and will gain weight quicker than do
The subject is in present tense so "required" should be require. Eliminated

(D) associate with other calves, they have required less medication and will gain weight more quickly than do
Needless use of perfect tense with the addition of "have".

(E) associate with other calves, they require less medication and gain weight more quickly than

associate is parallel with exercise, require is in the present tense. Correct.