Nullcheck
空检查
🗣️ 情景例句
Weren't they going to be here this morning?
他们不是今天早上要来这儿吗？
The classes are interesting, and the teachers are good.
那些课很有趣，老师又好。
and then there are three thousand million other Milky Ways, or galaxies, in the universe.
况且在宇宙中还有30亿个天河，即银河系。