precautionary
  (a.)預先警戒的,預防的,留心的
  Pre·cau·tion·a·ry a. Of or pertaining to precaution, or precautions; as, precautionary signals.
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  precautionary
       adj : taken in advance to protect against possible danger or
             failure; "gave precautionary advice"; "I would take
             precautionary steps to keep him away" [syn: precautional]