Great changes _______ in our hometown since 1980

Is this model plane________,Tom —-Yes,it is______.I made it by______.

They considered _____a computer, which was considered _____a great help in their work. [ ]

Mark has _____ good command of English. Therefore, he plays _____very important part in our team.

It is advised by health experts that windows should be opened now and then for air to _____, whichmakes the air in your room fresher. [ ]