To find the roots, we need the values of x that make the equation equal to zero. Here the quadratic is x^2 - 4x + 0 = 0. Look for two numbers whose product is 0 and whose sum is -4. Those numbers help us factor the expression, so each factor is set equal to zero. Solving the two simple equations gives x = 4 and 0. Therefore, the correct answer is 4 and 0.