Q1: Determine the values of A, B, C, and D that make the sum term equal to zero.

ANS:B - A = 1, B = 0, C = 1, D = 0

When you add a variable with 1 result will be equivalent to 1 as the Boolean logic A+1 = 1. Again, the result will be equivalent to variable when you'd add any variable with 0 according to Boolean 2nd logic A+0 = A (if A = 1, A + 0 = 1).

So it is proved that if we make any sum term equal to 0, value of every variable will must be 0 in that sum term. If we determine A = 0, it will be inverted into 1. But value 1 is not allowed for this term. So, the values will be A = 1, B = 0, C = 1 & D = 0.