Look at the picture. The motor symbol in the picture represents the electric fan. After reading the question, it is known that only cold air is supplied when switch S1 is closed, which means that the electric fan circuit is on, the heating element circuit is disconnected, the electric fan and the heating element are connected in parallel, and the switch is on the main road. B and D in the picture obviously do not meet the meaning of the question; the fall switch requires the heater to disconnect the power when it falls accidentally. Look carefully at pictures A and C. There is a spring in the switch. When it is placed normally, the spring is compressed by the gravity of the heater and the circuit is turned on. When a fall occurs, the switch disconnects the power supply under the action of elastic force. Figure A meets the requirements. Optional A
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