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!
Things of the same species have similar morphology and can INTERBREED
Fastest is o over a hundred knots per hour slowest is from under one knot per hour
I believe its A. I could be incorrect though.