According to the author, de Tocqueville was similar to many modern historians in his A. interest in the demographic differences between Russia and the United States during the nineteenth century B. failure to undertake a comparison of Russian serfdom and United States slavery C. inability to explain why United States slavery and Russian serfdom were abolished during the same decade D. overestimation of the significance of the political differences between Russia and the United States E. recognition of the essential comparability of Russia and the United States