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 ":".
A
lander
and
a
sample-return
to
Earth
were
options
under
study
.
A:O
lander:O
and:O
a:O
sample-return:O
to:O
Earth:O
were:O
options:O
under:O
study:O
.:O