On a narrow section with a steep gradient, without a priority sign, which does not allow two vehicles to pass, priority belongs to the vehicle travelling...

A)downhill.
B)at a higher speed.
C)uphill.Correct
On narrow sections with a steep gradient where, due to their narrowness, it is impossible or very difficult for two vehicles travelling in opposite directions to pass simultaneously, and where priority is not signposted, right of way belongs to the vehicle travelling uphill, except if it can reach a designated passing place first.
Sections with a steep gradient are understood to be those with a minimum incline of 7%.