Find the Matching Number from Among the Choices Listed Atbottom

Find the matching number from among the choices listed atbottom. You may use choices more than once, and be aware that there are more choices than you will use.
-___ alternation between stress and unstress

A) The Beatles
B) Philip Glass
C) Bill Haley and the Comets
D) "Ave Maria"
E) music
F) Renaissance
G) Scott Joplin
H) improvisation
I) chorus
J) spirituals
K) Lady Gaga
L) atonality
M) key
N) tone
O) pentatonic
P) baroque
Q) Duke Ellington
R) Eminem
S) plainsong
T) rhythm
U) symphony
V) U2
W) "White Christmas"