void setup() {
  Serial.begin(115200);
  Serial.println("Choose an option to display:");
  Serial.println("A: Print");
  Serial.println("B: Multiplication");
  Serial.println("C: LED ON/OFF");
}

void loop() {
  if (Serial.available() > 0) {
    char inByte = Serial.read();
    switch (inByte) {
      case 'A':
      case 'a':
        optionA();
        break;
      case 'B':
      case 'b':
        optionB();
        break;
      case 'C':
      case 'c':
        optionC();
        break;
      default:
        Serial.println("Error");
    }
    while (Serial.available() > 0) {
      Serial.read();
    }
  }
}

void optionA() {
  Serial.println("Hello, World!");
}

void optionB() {
  for (int number = 1; number <= 10; number++) {
    Serial.print(number);
    Serial.print(" x 2 = ");
    Serial.println(number * 2);
  }
}

int LED = 0;

void optionC() {
  LED = !LED; // Toggle the LED state
  if (LED) {
    Serial.println("Turning LED on");
  } else {
    Serial.println("Turning LED off");
  }
}