ANS:A - storm

An abrupt and sudden fall in the reading of a barometer is an indication of stormy weather. A barometer measures atmospheric pressure, and a sudden drop in pressure typically indicates the approach of low-pressure systems, which are often associated with stormy weather conditions. These low-pressure systems can bring about atmospheric instability, leading to the formation of clouds, precipitation (such as rain or snow), and potentially severe weather phenomena like thunderstorms, strong winds, or even tornadoes. Therefore, an abrupt and sudden fall in the reading of a barometer is commonly interpreted as a warning sign of impending stormy weather.