An even product hides the sign of the integers.
it may confuse. anyway OA is B
thre might be also an even number of odd integer, the product of which is odd.
i.e. -7*-9*-5*-1= 63*5 which is odd====4 numbers
this holds true also for -11*-9*-5*-7*-1====5 numbers
only the fact that the product is negative tells us that we must have an odd number of intgers