You can watch tv ...
A. After you have finished your work
B. If you have finished your work.
Which option is correct?
(A) is correct if the speaker knows the work is still going on.
(B) is correct if the speaker thinks the work may already have been finished.
They are both correct. But "U" isn't a word, and "tv" is an acronym (i.e. should be "T.V.").
If this was some type of homework, I would make sure that this is the question you are being asked.