Which of the following is an assumption on which the argument depends? A. cotton grass is the only one of the caribou's food sources that is becoming scarce as temperatures rise in arctic regions. B. caribou that do not eat enough protein to reproduce do not live as long as caribou that do C. The warming trend in arctic regions will not enable other plants capable of providing protein to caribou to grow there. D. The caribou is the only animal that depends on cotton grass as a major source of food. E. If the warming trend continues and cotton grass disappears from arctic regions, then cotton grass will be extinct.