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 ":".
The
abnormal
implantation
may
stem
from
the
maternal
immune
system
's
response
to
the
placenta
,
specifically
a
lack
of
established
immunological
tolerance
in
pregnancy
.
The:O
abnormal:O
implantation:O
may:O
stem:O
from:O
the:O
maternal:O
immune:O
system:O
's:O
response:O
to:O
the:O
placenta:O
,:O
specifically:O
a:O
lack:O
of:O
established:O
immunological:O
tolerance:O
in:O
pregnancy:O
.:O