Answer:
1) If a pesticide was used to kill the grasshoppers and the caterpillars, then the frogs should be fine, because the pesticide isn't made to effect them; also, unless their diet was only of grasshoppers and caterpillars, then the frogs would not starve.
2) Two human activities that can impact the ecosystem are, pollution, and deforestation. Pollution, because it can harm animals, but against popular (but unscientific) belief, doesn't cause climate change. Deforestation also harms animals, and also causes for some trees to have to produce more oxygen than before.
3)Life on earth could not exist on earth without plants and decomposers because there would be no oxygen left on earth for creatures to breathe, and there would be no nutrients to keep the earth alive.
I believe it is a ) stimulant.
I would say the answer is C. Hope I helped ^-^
