Stella solves the following system of equations using the substitution method.

y=−4x−65x−y=10

What is the single-variable equation she solves after substituting?
A. 5x−4x−6=10
B. 5x−(−4x−6)=10
C. 5x+10=−4x−6
D. 5x+10=−(4x−6)