What is the danger caused by fueling the vehicle while its engine is running?

1. There is no danger in keeping the engine running during vehicle fueling.
2. Correct answer: Combustion of fuel fumes by a spark.
3. When the engine is kept running, fuel consumption is increased.
4. Engine overheating might flare-up the fuel.

WhyA spark can ignite the fuel fumes. That is why the engine is turned off when refueling.