With no explanation, label each line with "O", "product-weapon", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
It
was
in
turn
replaced
by
anti-tank
guided
missiles
.
It:O
was:O
in:O
turn:O
replaced:O
by:O
anti-tank:product-weapon
guided:product-weapon
missiles:product-weapon
.:O