Which three types of air masses are needed to form a tornado? (pick 3)

warm, moist air
warm, dry air
cold, moist air
cold, dry air
temperate moist air
temperate dry air

warm, moist air

warm, dry air

and

cold, dry air

Explanation: Tornado alley has many tornadoes because of the warm, moist air from the Gulf of Mexico, the warm, dry air from southwest United states, and the cold, dry air moving down from Canada.

when the chinese communist party took power in 1949, it began to build new di and levees to hold the yellow and yangtze rivers back.

where is the picture? ?