Final answer:
Severe thunderstorms are characterized by hail measuring at least 0.75 inches in diameter and wind speeds of 58 mph or more, both of which are indicative of powerful updrafts and potential damage.
Step-by-step explanation:
The characteristics of a severe thunderstorm include elements that can cause significant damage or present hazardous conditions. Two such characteristics are Hail measuring 0.75 inches or more in diameter (C) and Wind speeds of at least 58 miles per hour (D). The presence of hail signifies severe updrafts within the storm system, which in turn indicates a strong thunderstorm. Moreover, high wind speeds are capable of causing property damage and are a benchmark for classifying a storm as severe.