The Supply of Nurses in Country a Is the Same

The supply of nurses in country A is the same as the supply in country B, but the nurses in country A earn 90% more than the nurses in country B. What can explain this difference?

A) The labor demand curve for nurses in country A is upward sloping.
B) Although the labor supplies are equal across the two countries, the labor supply curve in country A is downward sloping.
C) Country A's economy is more productive than country B's, so the demand for nurses is higher in country A.
D) Country A uses relatively more doctors than nurses to treat patients than country B.