Which of the Following Is a Simple Sentence

Multiple Choice

Which of the following is a simple sentence?

A) Although John taught James the piano, James is the better player.
B) James plays both the piano and the violin excellently.
C) James plays the piano well, but is not as skilled at the violin.
D) Though he studied the piano with a tutor, James learned the violin on his own.
E) James plays the piano well, but not as well as John.