If you were to use the substitution method to solve the following system, choose the new equation after the expression equivalent to x from the second equation is substituted into the first equation.

3x + 2y = −21
x − 3y = 4

A. 3(3y + 4) + 2y = −21
B. 3(−3y + 4) + 2y = −21
C. 3x + 2(3y + 4) = −21
D. 3x + 2(−3y + 4) = −21