The correct answer is option 3, i.e., input devices
The microphone, scanner, trackball, and joystick are examples of Input Devices.
The output devices include Monitors, Speakers, Printers, Headphones.
The different types of printers are Inkjet printers, Laser printers, Dot Matrix printers, Daisy-Wheel printers, etc.
CPU is the Central Processing Unit which performs all the basic functions like arithmetic, logic, controlling and input/output operations. This is the reason why CPU is termed as the 'brain of computer'.