Simplify the Expression Algebraically $$\sin ( 9 x + 9 y ) \sin ( 9 x - 9 y )$$

Multiple Choice

Simplify the expression algebraically.​ $$\sin ( 9 x + 9 y ) \sin ( 9 x - 9 y )$$ ​

A) $\sin ^ { 2 } x - \sin ^ { 2 } 9 y$
B) $\sin ^ { 2 } 9 x + \sin ^ { 2 } 9 y$
C) $\sin ^ { 2 } 9 x - \sin ^ { 2 } 9 y$
D) $\sin ^ { 2 } x + \sin ^ { 2 } y$
E) $\sin ^ { 2 } 9 x - \sin ^ { 2 } y$