You can do an exercise in writing or you can do it just by talking to each other, so it's an oral exercise. For example, the teacher could say: "Discuss this statement with your partner!", then the students would do this exercise verbally/orally.It doesn't make sense either way. Can you express the idea in different words?
I agree. Body language, tone of voice, etc. can all be "non-verbal" communication.
... symbols, numbers, and anything else that isn't words.
I frequently hear body language described as non-verbal communication.