Answer:
C. Leadville has a higher elevation.
Step-by-step explanation:
In those two cities depicted in the picture, one city being further west or east does not cause significant temperature change. (Too north or too south can change this but this is not what we are supposed to find.) Rules out A.
Latitude is basically where a city is on the map, either north or south, and they have the same latitude, so B doesn't make sense.
A difference between an average high and low does nothing to why it would be colder in one place over another.
C is the logical answer for this question. The elevation, or how high you're elevated, changes the temperature. The higher the elevation, the colder it becomes since you're more closer to the clouds, and the clouds are actually really cold. Did you know that? this is why we cannot breathe outside in airplanes, it is way too cold and not enough CO2 to survive.