将面粉、水和酵母的混合物放在温暖处静置四个小时。

The ___mixture of flour, water and yeast is then left in a warm place for four hours.

向混合物中加入牛奶，搅拌至顺滑。

Add milk to the ___mixture and stir until smooth.

混凝土是沙、水泥和水的混合物。

Concrete is a ___mixture of sand, cement, and water.