F4BIO

think about a cube
if a cube its side , width and height is 1, so its volume is 1^3 or 1
and its surface is 6(1x1) =6
if a cube it side is 8. then
its volume is 8x8x8=512
and its surface area is (8x8)6 = 384
therefore, that's why the volume increasing and its surface do not increase as much as or as fast as its organism
so, like cells, that''s why they will hv division, because the surface can not contain its big increasing volume

Answer for Q2.

The answer is not A, because cilia are small and tiny hairs in the trachea, that they can only stop small particles like dust and germs, rice is too big for cilia to action

The answer is not B, because mucus is a kind of sticky liquid secreted by our body to trap germs and bacteria and dust, but not big objects like rice

The answer is not C, because exhaling will just give out a normal amount of air which is not sufficient to stop the rice grain entering

So the answer is D, coughing, by definition, is a word to describe the action to exhale then inhale a large amount of air in a short time, the large amount of air exhange can thus stop the rice grain and exhale out from the trachea

Hope the above information can help