If you are talking about books, then there are two important American classics that were written in 1947, so I guess you can choose either one of them:
1. A Streetcar Named Desire, written by Tennessee Williams
2. The Pearl, written by John Steinbeck
If you are not talking about books, then you should tell us what you mean by classics.
Answer:
The answer is
D. They are choral music forms
good luck
To learn about the history of art
Answer:1/4 of a beat of sound. or 1/2 of a beat of sound
