Answer:
The correct answer is the maritime tropical air masses.
Step-by-step explanation:
These air masses are loaded with moisture with the water on which they are produced and heated as well. These air masses are form over the ocean in the hot areas of the Gulf of Mexico and the tropics.
Later they move towards the north, which brings an increase of humidity and hot winds to the United States. This phenomenon generates an increase in the probability of rains and generally occurs in the summer season in the southern states of the country. But nevertheless they can be formed throughout the year.