B and E are the corect answers. For a pair of numbers to be additive inverses, that means that the sum of the two numbers must be 0. And only a pair of opposite nunbers, such as 2 and -2, can have a sum of 0.
The first package is 4 oz (1/4lb) at 79cents = 19.75 cents/oz Second Package is 8 oz at 1.59 = 19.875 cents / oz So the first package is cheaper per ounce.