Brake oil pipe.
Iron pipes lead from the brake master cylinder to the brake cylinders of the left and right rear wheels. The two thicker ones are the gasoline inlet pipe and the oil return pipe, which are plastic pipes that connect the engine and the gasoline tank.
There are three pipes on the engine, two are the inlet and outlet pipes of the heater water tank, and one is a vacuum pipe connecting the engine intake pipe to the brake vacuum booster pump