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?
(A) 18
(B) 12
(C) 21
(D) 6
(E) 15
Since Ethan does not sit next to Dianne, the four must arrange themselves in one of the configurations:
$\mathrm{D} \_\mathrm{E}$
$\mathrm{D}$

- 
- $\mathrm{D} \_\mathrm{E}$
$\mathrm{E}-\mathrm{D}$
E
$\mathrm{D}$
$\mathrm{E}-\mathrm{D}$

For each of these six configurations, there are two ways for Beverly and Jamaal to sit (either with Beverly on the left or with Jamaal on the left).

Therefore, there are $6 \times 2=12$ possible ways that the four can sit. (Try listing them out!)

ANSWER: (B)