Outside the built-up area near Hardenberg you are driving on a quiet road where 80 km/h is allowed. It is dry and you have good visibility. You are doing 50 km/h and a queue of cars is forming behind you. What do you do?
You keep doing 50; you are well above the fixed minimum speed of 40 km/h
You speed up to a suitable pace; driving unnecessarily slowly hinders the traffic flow
You keep driving like this; slower is safer and whoever is in a hurry can overtake
Explanation
False — you assume a fixed figure for the lowest permitted speed. The book gives no such figure. What the book does say: do not drive unnecessarily slowly, because that hinders the flow and invites risky overtaking (Book p.121-122).