Why are opto isolators normally used between the microcontrollers and the ULN2803?

Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes. Mixed signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems. What inference can be drawn from the above?

A

All automatically controlled products and devices have microcontrollers.

B

Microcontrollers save money.

C

Both option 1 and option 2

D

Neither option 1 nor option 2

Why are ULN2803 normally used between the microcontrollers and the relays?

A

for increasing the voltage capability required by a relay

B

for switching purposes