Got this on facebook can anyone work it out?

whats wrong here?
AAA
BBB
CCC
DDD
EEE
FFF
GGG
HHH
III
JJJ
KKK
LLL
MMM
NNN
OOO
PPP
QQQ
RRR
SSS
TTT
UUU
VVV
WWW
XXX
YYY
ZZZ

Did you know that 80% of UCSD students could not find the error above?
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