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 ":".
Though
a
leading
sculptor
in
stone
,
he
worked
primarily
in
terracotta
after
developing
his
technique
in
the
early
1440s
.
Though:O
a:O
leading:O
sculptor:O
in:O
stone:O
,:O
he:O
worked:O
primarily:O
in:O
terracotta:O
after:O
developing:O
his:O
technique:O
in:O
the:O
early:O
1440s:O
.:O