The #if condition is evaluated only at compile time. The "if" is evaluated at run time.

if (condition1) {

  // Tue Task 1

}

else if (condition2) {

  // Tue Task 2

}

else {

  // Tue Task 3

}

if (condition1) {

  // do Thing A

}

else if (condition2) {

  // do Thing B

}

else {

  // do Thing C

}

if (condition) {

  //statement(s)

}

if (x > 120) {

  digitalWrite(LEDpin, HIGH);

}

​

if (x > 120) {

  digitalWrite(LEDpin, HIGH);

}

​

if (x > 120) {

  digitalWrite(LEDpin, HIGH);

}

​

if (x > 120) {

  digitalWrite(LEDpin1, HIGH);

  digitalWrite(LEDpin2, HIGH);

}

// Alle Anweisungen sind korrekt

pinMode(LED_BUILTIN, OUTPUT);