Monica: You will never see me naked.
Rachel: Since when?
Joey: Since always.
上下句是如此的。
还有就是，请问可以直接如此提问吗Since when?省略了主语，谓语...
谢谢老师解答
when可以是代词。比如《牛津》
when: pronoun
what/which time
Until when can you stay?
‘Ive got a new job.’ ‘Since when?’
所以，since when并没省略什么，= since what time.
since when...? 用来表示惊讶或生气。
《朗文》since when ...?
spokenused to show that you are very surprised or angry
Since when have you been interested in my feelings?