Many cars, motorcycles and other modern vehicles have fuel warning light devices. the warning light is usually red which switches on automatically when the level of fuel in the tank is very low. The warning light gives the driver information about the amount of petrol in the tank. When the light switches on red, it tells the driver that the petrol in the tank is almost empty. Therefore he have to put more fuel into the tank. However do you know how the fuel warning works?Well this is the way the fuel warning light work and gives the driver information about the accurate amount of the petrol in the tank. When the level of the fuel falls, the float inside the tank moves downwards. When this condition happens, the arm also moves downwards and it make the lever touch an electrical contact. This switches on the fuel light in the car dashboard.

What is the main idea of paragraph one?
a. The use of warning light on the vehicle
b. The warning light turn into red
c. The amount of the petrol in the tank
d. The way of the warning light works
e. The automatically of vehicle​