What is the least possible value of (x y-1)^{2}+(x+y)^{2} for real numbers x and y ?

**Answer Choices**

A. 0

B. \dfrac{1}{4}

C. \dfrac{1}{2}

D. 1

E. 2

What is the least possible value of (x y-1)^{2}+(x+y)^{2} for real numbers x and y ?

**Answer Choices**

A. 0

B. \dfrac{1}{4}

C. \dfrac{1}{2}

D. 1

E. 2