Final answer:
The function used to set a microcontroller pin to HIGH or LOW is the digitalWrite function, which is crucial for controlling output devices connected to digital pins.
Step-by-step explanation:
The function used to set any pin in the state of HIGH or LOW on an Arduino or similar microcontroller is digitalWrite. This function is essential in controlling output devices like LEDs, motors, and other components. For instance, to turn on an LED connected to digital pin 8, you would use digitalWrite(8, HIGH);, and to turn it off, you would use digitalWrite(8, LOW);.
Other options provided in the question serve different purposes. digitalRead is used to read the state of a digital pin, analogWrite is used to output a pulse-width modulated (PWM) signal to a pin, and pinMode is used to set a particular pin to be either an input or an output. Therefore, the correct answer is B. digitalWrite.