What most likely explains the differences in mortality rates between the United States and countries with higher rates, such as Russia?
A
The population of the United States is more scattered than the populations of countries with higher mortality rates.B
The United States is more isolated from other nations than countries with higher mortality rates.C
The disease reached the United States later than it reached countries with higher mortality rates.D
The United States adopted effective public health policies more quickly than countries with higher mortality rates.