With no explanation, label each line with "O", "organization-company", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
The
airport
serves
as
a
hub
for
American
Airlines
and
a
base
for
Southwest
Airlines
.
The:O
airport:O
serves:O
as:O
a:O
hub:O
for:O
American:organization-company
Airlines:organization-company
and:O
a:O
base:O
for:O
Southwest:organization-company
Airlines:organization-company
.:O