Topic: Dangling Modifer,

Best Answer Explained in Below-:

The sentence "What surprised me the most was how __ and reacted exactly like you," requires the correct grammatical form to complete the thought appropriately. The phrase "how __" signals a need for a clause that conveys the means of comparison concerning the subject 'he.'

Option C: "he looked" is the correct choice because it fits into the structure as a direct statement. The usage of "looked" in the simple past tense aligns with the surprise being expressed in the narrative—implying that the speaker is reflecting on a specific moment in time when 'he' looked in a certain way.

In contrast, Option A: "did he look" introduces an interrogative form which disrupts the declarative nature of the sentence. Option B: "does he look" suggests a generalization or habitual action, not fitting well with the context, which indicates a past experience. Finally, Option D: "could he look" implies a conditional or hypothetical scenario, which does not align with the factual observation being described.

Therefore, the choice of "he looked" seamlessly integrates into the sentence, maintaining the intended meaning and grammatical accuracy.