Answer: (D) All of the above answers are correct.
Step-by-step explanation:
All the given options are true about the use of courtesy. The courtesy is the type of formal gesture that helps driver for interaction on the road and also keep maintain and move the flow of the traffic on road. When we driving, the courtesy is useful when we constantly encompassed by the other street clients.
They are available in any event, even when we out of view, disguised by your vehicle's obstacle. The courtesy also improve interaction of the driver and helps in flow of the traffic.
Therefore, Option (D) is correct.