GDP cannot be used for international comparisons because a. countries are similar in the skills of the labor force. b. countries differ in the share of economic activity done in organized markets. c. countries differ in political structure. d. countries differ in population statistics.

While GDP is a widely used measure of economic performance, it fails to capture the complexities of different economies, particularly in terms of how much economic activity occurs outside of formal markets. This discrepancy can skew perceptions of a country's economic health and make comparisons with countries that have varying levels of informal economies misleading. Furthermore, GDP does not take into account differences in living costs and standards of living across countries, which can lead to significant misinterpretations. Countries with lower GDPs may provide better quality of life for their citizens due to lower costs, while those with high GDPs may have inflated economic figures that do not reflect the average citizen's real experience.