A short chain is usual attached to the back of a petrol tanker trailing behind it to ensure that the

A. petrol tanker is balanced on the wh eel
B. heat generated by friction in the engine can be conducted to the floor
C. charges generated by friction in the tanker can be conducted to the earth  
D. the tanker moves slowly as the chain touches the floor
E. chain produces sound for the resonance of the tanker engine

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Correct Answer: C