Sentence Correction

One benefit of learning to speak a language while learning to read it rather than separately is that the student can more effectively apply his or her knowledge in social settings.

(A) rather than separately
(B) rather than independently
(C) instead of separately
(D) instead of as separate processes
(E) rather than in a separate process

OA [spoiler] (E)[/spoiler]

there is a slight change in meaning between 'instead of' and 'rather than'.

'instead of' implies a substitution.
eg: I accidentally turned off the light instead of turning off the oven!

'rather than' implies preference.
eg. I like Tea rather than Milk.

in our question we are not talking about substitution but rather a preference of one method over the others.

now lets move to options:
(A) rather than separately [ separately is an adverb and it needs to modify something. it just cant be hanging as an independent word. Eliminated]

(B) rather than independently [same adverb error as in A]

(C) instead of separately [ too many errors. we dont require 'instead of' here and 'separately' needs to modify something]

(D) instead of as separate processes ['instead of' is not required here]

(E) rather than in a separate process [bingo! perfect choice.]

Hope this helps!

Every well explained