The everyday behavior of whales is particularly difficult to study because introducing novel stimuli, such as divers or submarines, into the whales' environment causes whales to behave in unusual ways. Some biologists plan to train sea lions to carry video cameras on their backs and, on command, to swim along with whales. They argue that since whales are accustomed to there being sea lions nearby, using the sea lions to film the whales would allow biologists to study the everyday behavior of the whales. Which one of the following is an assumption on which the biologists' reasoning depends? ['The trained sea lions will not be aware that they are carrying video cameras on their backs.', 'Whales will often react aggressively in the presence of divers and submarines although aggressive behavior is unusual for whales.', 'The behavior of the sea lions under human command will be within the range of sea lion behavior to which the whales are accustomed.', 'Sea lions carrying video cameras will be able to film whales at a much closer range than divers can.']