In full adder:
For input x, y and Ci
So = x ⊕ y ⊕ Ci
Co = xy + Ci(x + y)
For x = 1, y = 0 and Ci(carry input) = 0
i.e. So = 1 ⊕ 0 ⊕ 0 = 1.
Co = 1*0 + 0(1 + 0) = 0.
For x = 0, y = 1 and Ci = 1
i.e. So = 0 ⊕ 1 ⊕ 1 = 0
Co = 0*1 + 1(0 + 1) = 1.
So, option (A) is correct.