What causes the milky appearance when carbon dioxide is bubbled through limewater?

A high-scoring answer should explain explain that the milky appearance is caused by formation of a solid precipitate. Use method first, observation second, conclusion last: name the relevant test or measurement, state the observation, and then connect the result to Test for carbon dioxide.

This is correct because limewater is the evidence expected for carbon dioxide, and turns milky is the result that supports the conclusion. A complete answer should use the approved objective wording, include the relevant evidence, and avoid unsupported identification claims.