Which shows the rational expression written using the least common denominator? x+1/4x² + x+1/x²

a. x+1/4x² + 4(x+1)/4x²
b. x+1/x² + x+1/x²
c. x+1/x² + 4(x+1)/x²
d. x+1/4x² + x+1/4x²