Ответ:

1.he has already made a tree house

2.They (not/have) IT classes ( больше ничего не было? все в перфекте надо? если да, то "They have not had IT classes ")  

3. Have your friend ever met a ghost ?

Объяснение:

Ответ:

1. He has already made a tree house.

2. They don't have IT classes.

3. Have your friend ever met a ghost?

Объяснение:

1. He has ALREADY made a tree house- Present Perfect

2. They don't have IT classes- Present Simple

3. Have your friend EVER met a ghost?- Present Perfect