The correct answer is (A) To stir violently; to agitate fiercely; to stir (liquid) about, to make (the sea) froth; to wash to and fro, to foam, to seethe. Also, to produce butter by beating (milk or cream) in a churn.

Churn comes from Old English cyrne, cyrin.

Examples of use:

• The water churned in the wake of the large vessel.
• His ungraceful dive churned up the water in the small swimming pool.