There are 24 ways in which Beverly, Dianne, Ethan, and Jamaal can arrange themselves to sit in a row of four seats. In how many ways can Beverly, Dianne, Ethan, and Jamaal arrange themselves in a row of four seats so that Ethan does not sit beside Dianne?
Answer Choices
A. 18
B. 12
C. 21
D. 6
E. 15