The answer is indeed A.
The idea behind this problem is that copper and wood are very different from each other in terms of thermal conductivity.
More specifically, copper is a very good conductor of heat, and wood is a very poor conductor of heat.
So, you heat the rod where the two materials are joined together. The material with the higher thermal conductivity will allow heat to travel from the point of contact to the other end.
However, the metarial with the lower thermal conductivity will not allow heat to travel as well from the point of contact to the other end.
Because wood is a very poor conductor of heat, point Q will be the hottest because heat will remain concentrated at that point. This implies that the least amount of heat will make it to point P.
The copper part of the rod will not have a significant difference in temperature between point R and point S, because heat will be distributed along the length of the metal.