The correct formula used to find the distance \( D \) between two points \((x_1, y_1)\) and \((x_2, y_2)\) in a coordinate plane is:
\[ D = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \]
Among the responses you provided, this corresponds to:
\[ D = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \]
So, select that option.