With no explanation, label each line with "product-airplane", "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
The
base
is
the
current
home
of
the
B-2
Spirit
bomber
.
The:O
base:O
is:O
the:O
current:O
home:O
of:O
the:O
B-2:product-airplane
Spirit:product-airplane
bomber:product-airplane
.:O