Question

what was antoine henri becquerel studying when he discovered radioactivity?
phosphorescence
half - life
geiger counters
gamma radiation

Explanation:

Antoine Henri Becquerel was studying phosphorescence (specifically of uranium salts) when he discovered radioactivity. Half - life is a concept related to radioactive decay, Geiger counters are used to detect radiation (invented later), and gamma radiation is a type of radioactive emission. His work with phosphorescent materials led to the discovery of radioactivity.

Answer:

A. phosphorescence