請依下文回答第 31 題至第 35 題
         Locating suitable food is one of the pressing problems faced by animals. __31__ pets or pigs in factory farms,most animals must spend a large fraction of their waking hours locating food and extracting it from theirenvironment. __32__ the case of herbivores, this may seem simple at first thought, but it is seldom an easymatter of wandering about nibbling whatever __33__ is encountered. Not all plants are equally nutritious, andsome contain distasteful or even __34__ substances. Even grazing animals that need only abundant grass dopick and choose which patches are most worth __35__ and pay considerable attention to signs that food isavailable from particular plants. Active predators face more obvious challenges because they must not onlylocate but capture prey animals that seldom wait passively to be eaten but devote considerable effort to avoidingthat fate.
【題組】31
(A) In contrast to
(B) In relation to
(C) In addition to
(D) In league with