With no explanation, label each line with "O", "location-other", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
Nearly
all
of
the
natural
gas
hydrate
accumulations
identified
in
the
Nankai
Trough
region
occur
at
a
depth
of
around
290
to
300
meters
below
the
seafloor
(
1,240
meters
below
sea-level
)
.
Nearly:O
all:O
of:O
the:O
natural:O
gas:O
hydrate:O
accumulations:O
identified:O
in:O
the:O
Nankai:location-other
Trough:location-other
region:O
occur:O
at:O
a:O
depth:O
of:O
around:O
290:O
to:O
300:O
meters:O
below:O
the:O
seafloor:O
(:O
1,240:O
meters:O
below:O
sea-level:O
):O
.:O