Identify the correct set of statements.
(a) A sigmoid curve is a characteristic of living organisms growing in a natural environment.
(b) Differentiated cells can regain the capacity to divide, and it is termed as dedifferentiation.
(c) The plant growth regulators are small simple molecules of diverse chemical composition.
(d) Auxin was isolated by F.W. Went from the tips of coleoptiles of oat seedlings.
Choose the correct answer from the options given below.

A sigmoid curve is a characteristic of a living organism growing in a natural environment. It is typical for all cells, tissues and organs of a plant. When differentiated cells regain for division, it is called dedifferentiation. Plant growth regulators differ in chemical composition like auxins(indole compounds), kinetin (adenine derivatives), ABA (derivatives of carotenoids), gibberellic acid (terpenes), ethylene (gas). Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings.