$$

A microcontroller at$-$least should consist of :

Select one:

a$.$ CPU, RAM, I$/$O devices, serial and parallel ports and timers

b$.$ CPU, ROM, I$/$O devices and timers

c$.$ RAM, ROM, I$/$O devices, serial and parallel ports and timers

d$.$ CPU, RAM, ROM, I$/$O devices, serial and parallel ports and timers