Which best revises this sentence for clarity without changing its overall meaning?

During recent research, genetic researchers have isolated the gene that determines the natural times a
person sleeps and wakes.


A.
Genetic researchers recently isolated the gene that determines a person's natural sleep cycle.



B.
During research, genetic researchers have isolated the gene that determines the natural times a person sleeps and wakes.



C.
During recent research, genetic researchers have isolated the gene that determines times a person sleeps and wakes.



D.
During recent research, genetic scientists who research have isolated the gene that determines the natural times a person sleeps and wakes.