What will be the output of the following Java program?

class output 
{
    public static void main(String args[])
    { 
         StringBuffer c = new StringBuffer("Hello");
         StringBuffer c1 = new StringBuffer(" World");
         c.append(c1);
         System.out.println(c);
    }
}

A. Hello

B. World

C. Helloworld

D. Hello World

Answer: Option D