A barometer showing falling pressure indicates the approach of a（）.

单项选择题（）the canal transit，the radar was operating.

A.At
B.In
C.During
D.With

单项选择题（）should be used during the poor visibility if the radar’s screen shows heavy sea returns.

A.Gain Control
B.Brilliant Control
C.Anti-clutter Sea Control
D.Sweep Intercept

单项选择题（）is on the panel of radar.

A.KEYLOCK
B.REPEATER
C.STATIC INVERTER
D.ANTI-CLUTTER-SEA

单项选择题（）20 targets can be tracked at one time．When maximum tracking capacity is reached，no further acquisitions are possible.

A.As many as
B.So many as
C.As much as
D.As more as

单项选择题What will NOT induce errors into a doppler sonar log?（）

A.Increased draft
B.Pitch
C.Roll
D.Change in trim