I won't believe you until I've seen you in the room with my own eyes.
在时间和条件状语从句中，可用现在完成时态代替将来完成时。延续性动词可用于现在完成时，可接表示段的时间状语。非延续性动词也可用于现在完成时，但不接表示段的时间状语。有时在口语中，可用一般过去时代替现在完成时。有些动词，如hope, plan, mean, expect和think等有时可用过去完成时来表示一个本来打算做而未做，曾经设想而未实现的事情。在时间和条件状语从句中，过去完成时可代替过去将来完成时。
(1) He has got constant help from her since he has known her.
(2) I have never heard of her since she left.
(3) The vistors have stayed here for three days.
(4) The young man has joined the Party.
(5) I had intended to come over to see you, but was prevented from doing so.
(6) We would get into trouble as soon as the water had run out.
(1) When you _____[learn] computer, you'll find it a bridge to so much knowledge.
(2) The film _____[put] on at this cinema for three days.
(3) I _____[meet] him twice this morning.
(4) I _____[hear] of you before.
(5) This is the most wonderful film I ____[see}.
(6) In the last few years there _____[be] great changes in computers.
(7) She must _____[be] here last week.
(8) He should _____[let] us through the forest yesterday evening.
(9) The old man _____[live] here since 1980.
(1) have learned (2) has been put (3) have met (4) have heard (5) have ever seen (6) have been (7) have seen (8) have let (9) has lived