Which solution shown below contains an error? 3/x + 4/x² = 3x/x² + 3x

A) 3/x + 4/x² = 3x/x² + 3x
B) 3/x + 4/x² = 7/x²
C) 3/x + 4/x² = (3x + 4)/x²
D) 3/x + 4/x² = (3x + 4)/x