Why should a driver keep the bus's engine idling at a controlled, low level (or off, where required) during a lengthy loading process, rather than revving it?

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1. This concern applies only to buses equipped with a manual transmission
2. Excess engine noise or movement anticipation could distract from carefully monitoring students near the bus
3. Revving the engine is the recommended way to signal students that boarding is complete and it is time to sit down
4. Engine speed during loading has no bearing on student safety

Correct!

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