The correct option is C F. Addicot
Abscisic acid (ABA) is a naturally occurring plant growth inhibitor and an inhibitor of plant metabolism. It was first isolated by F. Addicot in 1963 from cotton fruits and named it Abscisin II as it was thought to promote abscission in plants.
H.H Cousins observed the release of volatile substances from spoiled fruits that aids in the faster ripening of fruits. The gaseous plant growth regulators were later identified as ethylene.
Skoog and Miller discovered cytokinin, which has a notable effect on cytokinesis.
E. Kurosawa identified gibberellins.