|A) too hot||B) heavy wind|
|C) a buildup of dark clouds||D) lightning|
Answer: C) a buildup of dark clouds
The first indicator of an approaching thunderstorm is a buildup of dark clouds.
A thunderstorm is a storm with lightning and thunder; it is usually produced by heavy rain, gusty wind, and the cumulonimbus cloud. The thunderstorm is made up of moisture, unstable air and lift.