Який б пересування у ссавцiв? ? ​

2 и 6 будут Past indefinite 
Остальные ,соответственно,- Present Perfect
I have built a house.
I have built a house when he came out of school
I have never built houses
I haven't built a house
Have you ever built a tower?
We built a house today
I have not yet learned words
We haven't made tutorials
They have never seen a crocodile
They haven't seen yesterday the crocodile

Так. На заметку.
Время Present Perfect обозначает действие, которое завершилось к настоящему моменту или завершено в период настоящего времени

Время Past Simple(indefinite) используется для обозначения действия, которое произошло в определенное время в и время совершения которого уже истекло

I think computer is very important invention in our life. This is one of the most necessary think. In the past they were very big not useful and expensive. But now every one can afford this beautiful think. Now in schools some teachers can give homework to special web-cite and pupils can see their marks and homework. And in our life computer uses even for work. Every Self-respecting company give to workers computers. Because human can forget very important document. But computer can't! And one more think why to workers gives computers is hard calculations. No one human can remember figure, that have one million numbers!
This arguments can proof the statement "Computer is important"