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 ":".
Trace
moisture
leads
to
formation
of
phosgene
.
Trace:O
moisture:O
leads:O
to:O
formation:O
of:O
phosgene:O
.:O