question: A cold front is formed when a cold air mass runs into what?
distractor3: dry air mass
distractor1: hurricane
distractor2: cool air mass
correct_answer: warm air mass
support: A cold front forms when a cold air mass runs into a warm air mass ( Figure below ). The cold air mass moves faster than the warm air mass. So the cold air mass lifts the warm air mass out of its way. As the warm air rises, its water vapor condenses. Clouds form, and precipitation falls. If the warm air is very humid, precipitation can be heavy. Temperature and pressure differences between the two air masses cause winds. Winds may be very strong along a cold front.