A dog's path

This task is about pathways that are equidistant from lines or points.

Question

a)  The local kennel club was doing dog obedience tests.
     The diagrams below show the paths taken by four different dogs. 
     The first test was to run between two poles.
     Which dog stayed the same distance away from both poles for the whole test?

Question

b)  In the second test the dog had to run between a pole and a fence.
     Which dog stayed the same distance away from both the pole and the fence for the whole test?