The Answer is D
I tried it, the getter (getMyString) method is auto called when you reference the variable

Correct answer is D :

public class myController {
public String myString;
public String getMyString() {return 'getmyString';}
public String getStringMethod1() {return myString;}
public String getStringMethod2() {
if (myString == null)
myString = 'Method2';

return myString;
}
}

// {!myString}, {!StringMethod1}, {!StringMethod2}, {!myString}
// getmyString , , "Method2" , "getMyString"