The Most Violent Stage of the Single-Cell Thunderstorm Is When

The most violent stage of the single-cell thunderstorm is when _________________.

A) cool,dry air is rising high.
B) updrafts and downdrafts operate side by side in the same direction.
C) warm,moist air is rising high and at the same time as cool,dry air is descending rapidly.
D) downdrafts drag in so much cool,dry air that it chokes off the updrafts of warm,moist air.
E) none of these choices are correct