I think this is just a difference between a longer and a more concise way of expressing something. Since the second choice does not change the meaning but is shorter than the first, it is the better choice of the two. Watch out for ones like this one, they appear here and there. For example, you would not say "They treat them as they do fish, as they do lions, as they do bears, and as they do tigers." Instead, you would say "They treat them as they do fish, lions, bears, and tigers." Also notice that you do not need to say "They treat them as they treat fish...." you can simly say "do."

I've come across this question today and as khurram says Kaplan's explanation is that D changes the meaning of the sentence.

Could someone explain how it changes the meaning?
Thank you in advance.

D says the parents treat the boys as 'they' would discipline daughters. Here, 'they' could mean the boys. So the parent will discipline the boys as the boys discipline daughters.

With E though, because of ellipsis, 'they' refers to the parents.

You could also pick E over D because it's less wordy.

It's about picking the best shade of grey.

Got it, thank you.

With E though, because of ellipsis, 'they' refers to the parents.

Hey axat, can u enlighten this part please?