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when習(xí)慣上不與現(xiàn)在完成時(shí)連用

■when 表示“何時(shí)”“什么時(shí)候”時(shí)，可用于過去時(shí)態(tài)或?qū)�來時(shí)態(tài)，但通常不用于現(xiàn)在完成時(shí)。如：

你什么時(shí)候和他首次見面的?

誤：When have you first met him?

正：When did you first meet him?

■但是，since when 可以與現(xiàn)在完成時(shí)連用。如：

Since when have you lived here? 你從什么時(shí)候起住在這里的?

Since when have you become active? 你什么時(shí)候開始變得積極了?

Since when do you read newspapers? 你什么時(shí)候開始讀報(bào)的?

That was in 1949, since when things have been better. 那時(shí)是1949年，從那以后情況就好些了。