String Answer;

void setup() {
  Serial.begin(9600);
  Serial.println("Enter your answer:");
}

void loop() {
  if (Serial.available()) {
    Answer = Serial.readStringUntil('\n');   
    Answer.trim();                           

    if (Answer == "Demo") {
      Serial.println("Correct Answer!");
    } else {
      Serial.println("Wrong Answer!");
    }

    Serial.println("Enter your answer:");    
  }
}