Answer:
B. They form over water with cool, moist air.
Step-by-step explanation:
The maritime polar air masses are large bodies of air and humidity originate as a continental air masses collecting moisture, cold and warmth from the ocean.
it is denoted by the acronym mP this large bodies forms over the Pacific Sea and the northern Atlantic Sea, it tends to be unstable carry with them cool moist and heavy rains reaching the continents.