Which chemical is most commonly used for artificial rain?

Correct answer: (c) Silver iodide

Explanation

Silver iodide (AgI) is the chemical most used for artificial rain (cloud seeding). Its crystal structure is very like that of ice, so its particles act as nuclei on which supercooled water droplets freeze and grow, until they are heavy enough to fall as rain or snow.

Dry ice (solid CO₂) and common salt are also used. Silver nitrate is used in the indelible ink put on voters' fingers.