If volatiles such as water vapor and carbon dioxide are added to a rock, what will happen to the melting temperature

The melting temperature of a rock will decrease

Explanation:

In the case when the water vapour and the carbon dioxide is added to the rock so the rock melting temperature would be reduced as if we added the salt  to an ice on a road so it reduced the temperature

Therefore according  to the given situation, the last option is correct

And, the rest of the options are wrong

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: