Active transport
a)	Releases energy	b)	Requires energy
c)	Produces ATP	d)	Produces a toxic substance

(b)

Active transport is the movement of a substance from a region of lower concentration to region of higher concentration i.e., against the concentration gradient. This process involves the movement of free-energy gradient, they require the expenditure of energy from the breakdown of ATP and are, therefore, sensitive to factors affecting metabolism.