Factor Out the Greatest Common Factor $$15 a ( a - b ) + ( a - b )$$

Multiple Choice

Factor out the greatest common factor.
- $$15 a ( a - b ) + ( a - b )$$

A) $16 a ( a - b )$
B) $15 a ( a - b )$
C) $( a - b ) ( 15 a + 1 )$
D) $\left( 15 a ^ { 2 } - 15 a b \right) + ( a - b )$