IV
The children are not watching TV. сказуемое - are not watching - present continuous
He will have started on his way back by the time you return. сказуемое - will have started - future perfect
They often play on Sunday. - сказуемое - play - present simple
V
1) may. Ты можешь курить здесь
2) must. Мы должны спешить.
3) be able to. Я не мог сделать это вчера.