Read the following sentence and choose the best alternative which should replace the italicized part of the sentence.

The tremendous insight of Einstein was that the passage of time does not appear to be the same while standing still as it does to a person traveling at a speed which is a significant fraction of the speed of light.

The part to be replaced in the sentence lacks parallel structure and clarity. The phrase "while standing still" does not match "as it does to a person travelling," making the comparison grammatically inconsistent.

Both parts of the sentence should be the same structurally and grammatically. Option B is the best choice because it ensures a clear and balanced comparison between two people. The phrase "to a person standing still as to a person traveling" correctly maintains parallel structure, making the sentence more readable and grammatically sound.

Option A: "While standing still" is not parallel to "as it does to a person traveling." Here, The phrase "while standing still" lacks context as to who is standing still

Option C: This is not incorrect, but the structure is unnecessarily wordy.

Option D: The phrase "while standing still" suggests a state of being, whereas "to traveling" refers to an action or process. For a proper comparison, both elements should be in the same grammatical form.

Option E: This option is close to being correct but introduces an inconsistency in verb tense. "Standing still" is a continuous action, whereas "who travels" suggests a habitual or general action.