Multiple choice Which of the following is a synthetic plant hormone? IAA 2, 4 - D GA Zeatin Reveal answer Fill a bubble to check yourself B Correct answer Explanation 2,4-D (2,4-dichlorophenoxyacetic acid) is a synthetic auxin widely used as a herbicide and plant growth regulator. IAA is natural auxin, GA represents gibberellins, and Zeatin is a natural cytokinin produced in plants.