1. Which of the following plant growth regulators is NOT produced commercially?

A. Abscisic acid

B. Ethylene

C. Auxins

D. Cytokinins

I'll look more into it, but it's either C or D

Explanation:

Auxins: Auxin is a plant hormone produced in the stem tip that promotes cell elongation

Cytokinins: Cytokinins promote cell division. They are produced in growing areas, such as meristems at tip of the shoot. Zeatin is a hormone in this class, and occurs in corn (Zea).