蛋糕如果不盖好会很快变得不新鲜。

Cake goes ___stale quickly if it's not covered.

早餐面包不新鲜，没有食欲。

The bread for breakfast was ___stale and unappetizing.

地下室里不新鲜的空气让人呼吸困难。

The ___stale air in the basement made it hard to breathe.