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 ":".
Undercarriage
was
retracting
,
but
there
were
no
flaps
,
which
the
large
wing
area
with
thick
airfoil
made
unnecessary
,
obviously
at
the
expense
of
speed
.
Undercarriage:O
was:O
retracting:O
,:O
but:O
there:O
were:O
no:O
flaps:O
,:O
which:O
the:O
large:O
wing:O
area:O
with:O
thick:O
airfoil:O
made:O
unnecessary:O
,:O
obviously:O
at:O
the:O
expense:O
of:O
speed:O
.:O