Joining two sentences into a compound predicate sentence using conjunction "and" [closed]
Either 1 or 2 is okay, and they mean the same. Starting from "The boys are playing football and the boys are enjoying themselves", you can conjoin two of the constituents that differ if everything else in the two original conjuncts is the same (including the reference of "the boys"). The eligible pairs are the VPs "are playing football" and "are enjoying themselves", and the inner VPs "playing football" and "enjoying themselves". The rule involved is called conjunction-reduction (which I have seen referred to here quite a few times).