Final answer:
Hector St. John de Crèvecoeur wrote "What is an American," exploring the American identity, while Mark Twain did not write "America was Schoolmasters" but was a prominent figure in American Literary Realism known for critiquing society and its values.
Step-by-step explanation:
The authors of "America was Schoolmasters" and "What is an American" are not explicitly mentioned in the question, suggesting a potential error in the titles referenced. However, based on the options provided, "What is an American" was written by Hector St. John de Crèvecoeur, which explores the American identity by depicting the new American as an individual from a melting pot of cultures with a new set of values divorced from European prejudices.
On the other hand, Mark Twain known for his significant contributions to American Literary Realism, never wrote a piece titled "America was Schoolmasters." Nonetheless, Twain authored several classics dealing with themes such as the critique of education, the reflection of societal issues like slavery, and a commentary on the Gilded Age. His works often provide a satirical look at American society and a critical view of its values and practices.