The phrase "taken aback" is an idiom that means to be shocked, surprised, or caught off guard.
I: Correct Usage - The professor's sudden anger surprised the student, which correctly reflects the idiomatic meaning.
II: Correct Usage - The soldiers were caught off guard by an unexpected turn of events, aligning with the meaning of the idiom.
III: Incorrect Usage - While the audience may have been amazed, "taken aback" implies shock or strong surprise rather than simple awe or intrigue.
Hence, option (e) Only I and II is the correct answer.