With no explanation, label each line with "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport", "building-hospital" or "building-hotel" preceded by ":".
Although
their
skin
had
turned
to
bark
,
they
were
able
to
speak
with
a
human
voice
by
rustling
their
leaves
.
Although:O
their:O
skin:O
had:O
turned:O
to:O
bark:O
,:O
they:O
were:O
able:O
to:O
speak:O
with:O
a:O
human:O
voice:O
by:O
rustling:O
their:O
leaves:O
.:O