Which one of the plant growth regulators would you use if you are asked to:(a) induce rooting in a twig, (b) quickly ripen a fruit, (c) delay leaf senescence, (d) induce growth in axillary buds, (e) ‘bolt’ a rosette plant (f) induce immediate stomatal closure in leaves. 
(a) auxins(b) ethylenne(c) cytokinins(d) cytokinins (e) gibberellins(f) abscisic acid.
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