Qt A

$(a + b - 1)(a + b - 1) = a^2 + ab - a + ab + b^2 - b - a - b + 1 = a^2 + b^2 + 2ab - 2a - 2b + 1$

Qt B

$(a + b + 1)(a + b + 1) = a^2 + ab + a + ab + b^2 + b + a + b + 1 = a^2 + b^2 + 2ab + 2a + 2b + 1$

By comparing both quantities, and removing common terms, we will have

Qt $A = -(a + b)$

Qt $B = a + b$

We don't know the signs of $a$ & $b$, hence we can't decide.

Answer $D$