Can small trees contribute oxygen?

Yes, because even though other trees produce more oxygen, the small trees will still produce some oxygen. On top of this there are more small trees than big trees, so even though they make less oxygen, in whole they end up making more when added together!

No that answer is wrong. you have written the function of mitochondria in chloroplast and function of chloroplast in mitochondria.

True statement gravity force is more on bigger mass, less on smaller mass.all mass fall on planet with same acceleration and speeds