How is radioactive decay related to half life?

Half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive ..

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.