Final answer:
In the case of a cutting, cytokinin stimulates the growth of adventitious shoots, and auxin promotes the growth of adventitious roots. So, the correct answer is option a.
Step-by-step explanation:
The plant hormones that stimulate adventitious shoots and roots in cuttings are auxin and cytokinin, respectively. Auxin, like Indoleacetic acid (IAA), is widely used in plant nurseries for promoting the growth of adventitious roots on cuttings and cytokinin promotes cytokinesis, which is essential for shoot differentiation and development. In the context of the student's question, the correct answer is: auxin stimulates adventitious shoots and cytokinin stimulates adventitious roots of cutting, which corresponds to option b) cytokinin / auxin.
So, the correct answer is option a.