Use your brain power :
Why is yoghurt mixed in the batter or dough for making rava-idli, bhature, naan.

Explanation

Yoghurt contains useful bacteria. They cause fermentation in the batter or dough if added in proper proportion. In this process, the heat, carbon dioxide and other gases are produced. This helps the flour to rise. The vitamin content also increases and the preparations become tasty and light. Therefore, is yoghurt mixed in the batter or dough for making rava idli, bhature, naan.