豆腐在素食食谱中可以作为肉类的替代品。

Tofu can be used as a meat ___substitute in vegetarian recipes.

维生素不应被用作健康饮食的替代品。

Vitamins should not be used as a ___substitute for a healthy diet.

我一意识到舞台上有个替补，就非常失望。

As soon as I realized there was a ___substitute on the stage, I was really disappointed.