Human beings can exhibit complex, goal-oriented behavior without conscious awareness of what they are doing. Thus, merely establishing that nonhuman animals are intelligent will not establish that they have consciousness. Which one of the following is an assumption on which the argument depends? ['Some intelligent human behavior is neither complex nor goal-oriented.', 'All forms of conscious behavior involve the exercise of intelligence.', 'Complex, goal-oriented behavior requires intelligence.', 'The possession of intelligence entails the possession of consciousness.']