Which of the following is a cytokinin?

Answer: Option B

Zeatin is a cytokinin among the given options.
Cytokinins (CK) are a class of plant hormones that promote cell division, or cytokinesis, in plant roots and shoots.
Zeatin is a cytokinin derived from adenine, which occurs in the form of a cis- and a trans-isomer and conjugates. Zeatin was discovered in immature corn kernels from the genus Zea. It promotes the growth of lateral buds and when sprayed on meristems stimulates cell division to produce bushier plants.