The single idea being tested is the difference between strengthening and weakening a behaviour in learning theory. Three of the choices push a behaviour up; one pushes it down, and that one is the answer to an except question.
Reward is plainly the addition of something desirable, which makes the behaviour more likely. Negative reinforcement is often misread, but it too raises behaviour: it works by taking away an unpleasant state when the behaviour occurs, so the person repeats the behaviour to gain relief. Operant conditioning is simply the umbrella principle (consequences shape behaviour) within which reinforcement boosts a response.
Punishment stands apart. Its entire purpose is to make a behaviour less frequent by applying an aversive consequence or by withdrawing a pleasant one. It is a behaviour-decreasing tool, not a behaviour-increasing one.
Hence, of the four, only punishment fails the criterion of increasing behaviour.
\[\boxed{Punishment}\]