With no explanation, label each line with "O", "location-bodiesofwater", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
The
Severn
has
historically
been
a
very
important
and
busy
river
,
and
has
been
bridged
throughout
history
.
The:O
Severn:location-bodiesofwater
has:O
historically:O
been:O
a:O
very:O
important:O
and:O
busy:O
river:O
,:O
and:O
has:O
been:O
bridged:O
throughout:O
history:O
.:O