Which of the following air masses would be warmer and more humid?

The air mass described as warmer and more humid is Maritime Tropical. This classification refers to air masses that originate over warm ocean waters, typically in tropical regions. As these air masses travel, they retain moisture from the ocean surface, which leads to higher humidity levels. The warmth of the ocean contributes to the overall temperature of the air mass, making it both warm and humid.

In contrast, Continental Polar air masses form over land in polar regions and are characterized by cold and dry air. Continental Arctic air masses also develop over land in colder areas and are even colder and also dry. Maritime Arctic air masses, while they originate over oceans, are typically found in colder regions and hence do not have the warmth associated with Maritime Tropical air masses. Therefore, when considering the definitions and characteristics of these air masses, Maritime Tropical distinctly stands out as the one that is both warm and humid.