When a mass of extremely cold, dry air moves over the ocean, it is likely to become a maritime polar air mass.
This is because maritime polar air masses form over cold ocean waters, and when cold, dry air moves over a relatively warmer ocean surface, it can pick up moisture, becoming moist and cooler air. The other options do not fit the scenario as well:
- Continental arctic air comes from land and remains dry and cold.
- Continental tropical air is warm and dry, originating from land over warmer regions.
- Maritime tropical air is warm and moist, typically associated with warmer ocean waters, not cold, dry air moving over the ocean.
Therefore, the correct answer is maritime polar.