I need to know what the answer is

Answer asap 50 points which of the following illustrates how a venus fly trap senses that an insect has landed in its open leaves? 1. using tiny hairs, the leaves sense a change in light. 2. using tiny hairs, the leaves taste a chemical. 3. using tiny hairs, the leaves detect a touch. 4. using tiny hairs, the leaves sense a change in water levels.