给多音字组词。

降：jiàng____     xiáng____

落：là____      luò____

—Could you tell me_    it's polite to eat noisily in Japan, Kumiko?

                               —Sure! It's polite to do that. It means you like the food very much.

气体的收集方法是由其性质决定的，氧气的收集（　　）

所有的自然数不是奇数就是偶数。