Which of the following statements is true? choose one:
a. tornado alley, an area of frequent tornadoes, runs along the gulf coast from mississippi to florida.
b. doppler radar cannot "see" rain or wind, so tornadoes are difficult to track.
c. tornadoes result when opposing updrafts and downdrafts push on existing horizontal cylinders of rotating air and tilt them upright.
d. tornadoes occur most frequently during the fall months.