Readtheparagraphanddecideonthebestchoice.根据段落意思，选择正确选项。Themainelementsrequiredforsurvivalarefood,fire,shelterandwater.Theirorderofimportancewilldependuponwhereyouhappentobe.Inthedesert,waterwillheadthelist;inpolarregionsshelterandfirewillbethemainconcerns.Orderingyourprioritiesisthefirststeptosurvival.Thefactorwhichdecidestheorderofimportanceforthemainelementsrequiredforsurvivalis_____.
