The correct answer is D. Normal speed.
The patrolman is a professional who is responsible for ensuring the safety of the public. They are trained to respond to emergencies and to take action to protect people and property. It is important for them to be able to travel at a normal speed so that they can reach their destination quickly and safely.
The other options are not correct because they are not speeds that a patrolman would typically travel at. A speed of 10 kmph is too slow, and a speed of 40 kmph is too fast. A patrolman needs to be able to travel at a speed that is safe and that allows them to reach their destination quickly.
Normal speed is the speed at which a patrolman would typically travel. It is a speed that is safe and that allows them to reach their destination quickly.