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.