Unavailability
[计] 无效性, 不可用性
🗣️ 情景例句
I'm delighted to make your acquaintance.
认识你我觉得非常高兴。
I'm two years younger than my sister.
我比我姐小两岁。
Yes, but what are in the boxes?
哦，那箱子里是什么呢？