If several fixed navigational lights are visible at the same time，each one may be positively identified by checking all of the following EXCEPT what against the Light List?（）

A.Magnetic compass table
B.Magnetic meridians
C.Isogonic lines
D.Variation is not indicated on small-scale nautical charts

A.accurate only in the Polar regions
B.accurate electronic servomechanisms
C.hand operated
D.accurate only if the vessel is underway