Conditions Necessary to Turn an Ordinary Thunderstorm into a Tornado-Spinning

Multiple Choice

Conditions necessary to turn an ordinary thunderstorm into a tornado-spinning monster include _______________.

A) a low-altitude,northerly flow of warm,humid,tropical air from the Gulf of Mexico
B) a cold,dry air mass moving down from Canada or out of the Rocky Mountains at > 50 mph
C) jet-stream winds racing east at speeds in excess of 150 mph
D) All of the choices are correct.
E) a low-altitude,northerly flow of warm,humid,tropical air from the Gulf of Mexico and a cold,dry air mass moving down from Canada or out of the Rocky Mountains at > 50 mph only