When riding a motorcycle, is it permitted to wear the helmet unfastened?

When riding a motorcycle, is it permitted to wear the helmet unfastened?
A)Only on urban roads, if the speed is below 40 km/h.
B)Yes, when it is a full-face helmet.
C)No, under no circumstances.Correct
The helmet must fit snugly on our head, it must not be tilted backwards or forwards, and the safety strap must always be fastened.