A difference between the innate immune system and the acquired immune system is

(a) the innate immune system includes many more different types of receptors than the acquired immune system.

(b) the acquired immune system response is immediate, whereas the innate immune response is delayed, peaking about 3 to 5 days after exposure.

(c) the acquired immune system retains a memory for past exposure, with subsequent responses being faster and more aggressive; the innate immune system does not.

(d) each acquired immune system cell responds to more different pathogens than each innate immune system cell.