Which plant hormone is basic in nature?
(a) Gibberellin
(b) Auxin
(c) Ethylene
(d) cytokinin

Hint plant hormone Help in ripening of fruit, wilting of leaves ,formation of leaves ,flower stem etc. Some plant hormones are ethylene , cytokinin ,gibberellin and auxin. In which gibberellin ,auxin are acids and ethylene are organic compounds and cytokinin has amino purine adenine.

Complete answer: To answer this Question you must know the chemical nature of plant hormones.
Hormones are chemicals produced by plants that regulate the growth processes. Some plant hormones are auxin ,cytokinin , gibberellin ethylene, and abscisic acid.
Gibberellin is also called gibberellic acid ,since it is acid itself so it is acidic in nature. The chemical formula of gibberellins is C19H22O6. It is responsible for promoting growth and elongation of cells in plants.
The most widespread auxin is indoleacetic acid ,simply IAA. It is derived from the amino acid tryptophan. All auxins are compounds with an aromatic ring and a carboxylic acid. Since it is derived from acid, it is acidic in nature.
Ethylene is a small hydrocarbon , a colourless flammable gas which is denoted by formula C2H4. It is the simplest alkene , used in the chemical industry. Polythene is usually made up of ethylene.
Cytokinin is a compound derived from a nitrogen containing compound (adenine). The chemical name of cytokinin 4- hydroxy-3-methylbut-2- enyl amine, is basic in nature. It helps in cell division by stimulating the process of mitosis.

Thus from the above statement it is clear that the correct option is (D) cytokinin.

Note: plant hormones are also called phytohormones . They act as signal molecules produced within the plant . phytohormone are found not only in higher plants, but in algae too, they also occur in fungi and bacteria also ,where they may be used to induce beneficial reactions in host plants.