$\quad\quad\quad\quad\text { Country A }$ $\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\text { Country B }$

$\quad\quad\quad\quad\text { Country A }$$\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\text { Country B }$
$\begin{array}{|l|l|l|l|}\hline \begin{array}{l}\text { Good } X \\(\text { units of } X) \end{array} & \begin{array}{l}\text { Good } Y \\(\text { units of } Y) \end{array} & \begin{array}{l}\text { Good } X \\\text { (units of } X) \end{array} & \begin{array}{l}\text { Good } Y \\(\text { units of } Y) \end{array} \\\hline 0 & 16 & 0 & 12 \\\hline 2 & 12 & 2 & 9 \\\hline 4 & 8 & 4 & 6 \\\hline 6 & 4 & 6 & 3 \\\hline 8 & 0 & 8 & 0 \\\hline\end{array}$
-In the table above, country B is producing 4 units of X and 6 units of Y. For country B, the opportunity cost of producing an additional unit of Y is

A) 2/3 unit of X per unit of Y.
B) 3 units of X per unit of Y.
C) 1/2 unit of X per unit of Y.
D) 2 units of X per unit of Y.