Which stroke or style is usually swum in a warm-up?

The #1 stroke referred to in the warm-up is the stroke you're focusing on in the upcoming session, your main event this session. After sitting around for an hour or so waiting for your event, it's important to wake up the muscles and increase the blood flowing through your body again.

thinking it would be d not too sure but i think it's right

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.