I worked on it seeming to be the least wrong.
a) had the axes mixed up,
b) could be right
c) the RA receives information from the ground correct as far as it went
d) just nonsense.
This left b) and c) as the only two that could be right and as I was not sure of the shape of the cone, decided to plump for the least technical.
Anyway, they told me that answer a) was the correct one - which makes me wonder whether I am mad or they are mad.