The correct options are
A Electric discharge happens between two oppositely charged clouds.
B Electric discharge happens between clouds and ground.
D The clouds acquire charge due to friction with air molecules.
During lightning, the clouds that acquire charge due to friction with air molecules induce opposite charge on other uncharged clouds. When these charges build up heavily on each cloud, they tend to discharge to other clouds or onto the ground. This electric discharge is seen as bright white streaks in the form of lightning.