Peter was so excited _______ he received the invitation to the important meeting.
A:that
B:though
C:when
D:before
56÷(7×8)=____
如图,AB为⊙O的弦,⊙O的半径为5,OC⊥AB于点D,交⊙O于点C,且CD=1,则弦AB的长是____.