With no explanation, label each line with "O", "product-train", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
They
were
high-density
units
,
externally
very
similar
to
the
Class
116
.
They:O
were:O
high-density:O
units:O
,:O
externally:O
very:O
similar:O
to:O
the:O
Class:product-train
116:product-train
.:O