Ella simplifies (3b+4r)+(-2b-r) and says the result is b+5r. What error did Ella make?
A. Ella incorrectly combined the b coefficients. The correctly simplified expression is 5b+5r.
B. Ella incorrectly combined the b coefficients. The correctly simplified expression is -b+5r.
C. Ella incorrectly combined the r coefficients. The correctly simplified expression is b-5r.
D. Ella incorrectly combined the r coefficients. The correctly simplified expression is b+3r.