The helmet must be replaced when...
A)the colours have gone out of fashion.
B)you change your motorcycle.
C)it receives any blow, as it may have been damaged.Correct
When the helmet has received a blow, whether in an accident or from falling from a height greater than 1.50 metres, it is advisable to replace it as soon as possible. In some cases, the damage suffered by the helmet is not visible to the naked eye.