如果你不把苏打水瓶的盖子盖回去，它就会跑气变淡。

If you don't put the top back on the soda bottle, it will go ___flat.

这啤酒开得太久，尝起来完全没气了。

The beer had been open too long and tasted completely ___flat.

庆祝会上，走了气的香槟令人失望。

The ___flat champagne was a disappointment at the celebration.