Simplify these expressions.
A$2 r+3+4 r$
B$8+3 d+d$
C$m n+(-3 m n)+6$
D$10 s+(-10)+(-4 s)$
A$2 r+3+4 r$
B$8+3 d+d$
C$m n+(-3 m n)+6$
D$10 s+(-10)+(-4 s)$