Approximately what percent of tank space should be left for expansion of oil due to possible temperature increase?（）

A.bunker at a normal rate
B.check for kinks in hose
C.close valves slowly
D.shut valves before topping off

A.lining up the systems
B.topping off 
C.starting delivery
D.connecting hoses and joints

A.draft of the vessel
B.rate of delivery
C.communication with terminal personnel
D.observation of manifold valves