The capacity to follow instructions of a parallel processor is not limited by the speed at which its components can operate but by its ability to integrate the work of each component.
GRAMMATICAL CHECK - Looking at the non-underlined part of the sentence, we can see
but by which hints for parallelism. Thus limited should be followed by
BY rather than TO. Therefore - B and C are out, leaving us with A, D, and E. Check the RED for reasoning.
(A) The capacity to follow instructions of a parallel processor is not limited by -
the placement of prepositional phrase (of a parallel processor) is incorrect. It should be right next to the subject (CAPACITY) to modify correctly.**Had the option been - The capacity of a parallel processor to follow instructions is not limited by, this option would have been correct but E would have still won over because of the concise phrasing.**(B)
The capacity to follow instructions in a parallel processor is not limited to (C)
The capacity to follow instructions in a parallel processor are not limited to(D) A parallel processor's capacity to follow instructions are not limited by -
SV Error - Capacity should have singular verb (IS instead of ARE)(E) A parallel processor's capacity to follow instructions is not limited by -
CORRECT - Concise and meaning clarity.***Also, in the non underlined part, its components and its ability correct refers to the parallel component's as ITS is a possessive pronoun.***