Did you know that most times if you put them all into one box then hit done it will keep the ones you got right and pull out the wrong ones. There are only two possible choices for each on. anyway.
1,2,5,6 goes with outdoor pollution.
and 3,4 go with indoor pollution.
I hope I helped.
I think the answer is REM sleep but look it up to be sure
An individual center of gravity is usually found A. Just above the belly button.
Hope I could help! :)
The answer is a because I just took this quiz (2020) I hope this helps