“I've been in the Dance Club since last February”中,“last”是什么

“I've been in the Dance Club since last February”中,“last”是什么 为什么I've been like this since last week不能变成I've liked this si I've been living in Sally's flat_____the last month. As you write in the sky,it has been 20 years since I last sa I have been in CZ since last year.这话对么?been in后可加since吗 The moment I've been looking forward to()at last I've been trying to learn how to play basketball since last he has been in english since last We‘ve been working hard for the last five years.中the last有什么 刚才所说延续性动词,例如i have been in Hong Kong since last week. It’s been quite some time since I was last in London How long have you been in Sydney?Since last Wednesday .I ___