Alejandro was asked to solve a system of linear equations by using the substitution method. What is the error in his work below? Step 1: 4y+x=15 -9x + 5y = 20 Step 2: 4y+x= 15 x = 15 - 4 Step 3: 4y + x = 15 4y + (15 - 4y) = 15 4y + 15 - +y = 15 There are infinitely many solutions to the system of linear equations Select one: © A. He substituted the expression he found in Step 2 back into the incorrect given equation. O B. He did not write both equations in slope-intercept form 6 C. His last step means that the system has no solution, not infinitely many solutions. O D. He chose the wrong given equation to solve for one of its variables in Step 2