已知：等腰△ABC内接于半径为6cm的⊙O，AB=AC，点O到BC的距离OD的长等于2cm．求AB的长．

Bulkheads which from part of the tanks on a vessel are stiffened to withstand（）.

A.deck loads from above

B.dynamic forces while afloat

C.hydrostatic pressure

D.over-pressurization