Which expression is equivalent to cos(A+B) cos(A-B)

When plugging in cos a+b and cos a-b how to I simplify to get one of these answers

answers are

COs(A + B) Which expression is equivalent to COS(A - B) . V 1 + tan A tan B O 1 - tan A tan B 1 - tan A tan B O 1 + tan A tan B O cos A sin B sin A cos B