Which function in Arduino is used to start serial communication over the COM port?

• A. Serial.available()
• B. Serial.begin()
• C. serial.begin()
• D. setup()

Answer: (B)

Initializing serial communication is done with Serial.begin, which opens the USB‑serial connection (the COM port) and sets the speed at which data will be sent and received. This call configures the baud rate you choose and enables the TX and RX paths so the Arduino can talk to a computer or another serial device. It’s typically placed in setup() so the link is ready as soon as the program starts, and the chosen baud rate must match the device on the other end to ensure data is interpreted correctly. Other options don’t start the serial link: reading functions like Serial.available() only check for incoming data, the lowercase version serial.begin() is not valid in Arduino because the Serial object uses a capital S, and setup() is the initialization routine where you would call Serial.begin but it isn’t by itself the function that starts serial communication.