Differences in temperature between two air masses causes (2 points) rain high pressure systems the jet stream cold fronts

The overall best answer is the jet stream. That forms along areas of strong horizontal temperature gradients in the mid and upper atmosphere. If the question is referring to surface air masses it's a little more difficult. It would be a cold front if the colder air mass is advancing into the warmer air mass. Rain does not always occur in this situation.

your answer should be c) enjoy!