问题如下：
Suppose three countries produce rulers and pencils with output per worker per day in each country as follows:
Which country has the greatest comparative advantage in the production of rulers?
选项：
A. Mexico.
B. Brazil.
C. China
解释：
A is correct.
Mexico has the lowest opportunity cost to produce an extra ruler. The opportunity cost is 2 pencils per ruler in Mexico, 3 pencils per ruler in Brazil, and 4 pencils per ruler in China.
考点：比较优势
解析：墨西哥生产1把尺子的价格是2个铅笔，巴西生产1把尺子的价格是3个铅笔，中国生产1把尺子的价格是4个铅笔，所以墨西哥具有最大的比较优势。
题里说output per workerper day，那表格里的数字不是代表产量么，选c