ANS:C - storm

A sudden fall of atmospheric pressure by a large amount is typically an indication of an impending storm. When atmospheric pressure drops rapidly, it often indicates the approach of a low-pressure system or storm. Low-pressure systems are associated with unsettled weather conditions, including rain, strong winds, and sometimes thunderstorms or other severe weather events. As the pressure drops, air rises and cools, leading to cloud formation and potentially precipitation. The rapid drop in pressure can be an early warning sign of approaching adverse weather conditions, prompting meteorologists to issue warnings for storms or other severe weather events. Therefore, a sudden fall of atmospheric pressure by a large amount is commonly associated with the onset of a storm.