Question

Motorcyclists need extra space on

wet or icy roads.

metal surfaces and railroad crossings.

on gravel and pavement seams.

all of the above conditions.

Answer 1

The motorcyclists need extra space on all of the given choices. That is because at these spaces, the motorcyclists need to be extra careful and a bigger space will help them do just that. The answer is therefore, the fourth choice. 

Answer 2

Motorcyclists need extra space on all of the above conditions.
If the roads are wet or icy, obviously the motorcyclists will need more space so as not to slide off the road and into a car to create a collision. If there are metal surfaces and railroad crossings, they will also need more space so as to cross them faster. In case of gravel or pavement seams, which can cause the motor to swerve, they need more space so as to avoid that.