Ifndef
如果未定义
🗣️ 情景例句
Speaking of being a mother,
谈到当母亲，
That night we partied until dawn.
那晚我们痛饮到天亮。
Then the bees left the hive and went to the feeding place.
然后那些蜜蜂离开蜂箱，飞到喂食点去。