The Table Shows the Number of Rubies and Diamonds That

The table shows the number of rubies and diamonds that Botswana and Namibia can mine using one day of labor. The opportunity cost of mining one diamond is _____ in Botswana and _____ in Namibia, and _____ has a comparative advantage in diamond production.
$\begin{array}{lclc} & \text { Rubies } & & \text { Diamonds } \\\text { Botswana } & 90 & \text { or } & 30 \\\text { Namibia } & 80 & \text { or } & 20\end{array}$

A) 0.33 ruby; 0.25 ruby; Namibia
B) 0.33 ruby; 0.25 ruby; Botswana
C) 3 rubies; 4 rubies; Namibia
D) 3 rubies; 4 rubies; Botswana