5a
1.is 2.is 3.am having 4.like 5.invite 6.are 7.is playing 8.buys 9.are dancing 10.take 11.is feeding 12.likes 13.am opening 14.are 15.am 16.are having
5b
1.He doesn't invite his parents to the party.He invites his friends.
2.Pete isn't feeding Jack's dog.His best friend (Jack's best friend) is feeding Jack's dog.
3.Jane and Linda can't sing very well.They can dance very well.
4.They don't take singing lessons.They take dance lessons.
5.Jack's best friend doesn't like computer games.He likes animals.
6.Jack's presents aren't boring.They are cool.
7.The children aren't having problems.They are having a lot of fun.