Which ARPA data should you use in order to determine if a close quarters situation will develop with a target vessel? （）

A.enhance weak target echoes and brighten them on the PPI
B.reduce clutter over the entire PPI by shortening the echoes
C.only suppress weak targets to a limited distance from the ship (sea clutter)
D.reduce the beam width to provide a map-like presentation for navigation

A.Immediately after floating free
B.After about one hour when the salt water activates the battery
C.Only when keyed by the radar of another vessel
D.Only when daylight activates the photovoltaic cell

A.the best fix is obtained by using a tangent bearing and a range
B.and using two radar ranges for a fix，the objects of the ranges should be close to reciprocal bearings
C.and using ranges，the most rapidly changing range should be measured last
D.and crossing a radar range of one object with the visual bearing of a second object，the two objects should be 80°to 110°apart