A:x2+(y−2)2=1
B:x2+(y+2)2=1
C:x2+(y−3)2=1
D:x2+(y+3)2=1
如图,∠ XOY=900,OW平分∠XOY,PA⊥OX,PB ⊥OY,PC⊥OW.若OA+ OB+OC=1,则OC=( ).
This box is_______ that one.