The rain began early in the morning. it fell as hard drops, one after another. the sky full of dark purple clouds. thunder began as a soft rumble and became louder and louder. lightning crashed every few minutes, making the sky a brilliant white.

The main idea is "the storm was very strong".

Explanation:

Storm is a generic term which covers a wide range of atmospheric disturbances from wind and wind disturbances, simple rain showers and snowstorms to thunderstorms. It is a meteorological phenomena in which heavy rain and wind because of moisture in the air is general.

The storm was very strong and powerful, as the start of the morning took place with heavy rainfall and hard drops. The scenario became more horrible when purple clouds start getting visible even after such a long duration of rain whereas thunder emerges with heavy sounds.

b or c im pretty sure