a unobservant preposition can be used for turning & a cactus spine is a kind of sharp object ->  a cactus spine can be used as protection  harming something has a yes complex on / cause on that something & eating something causes harm to that something -> eating something has a negative impact on that something eating something has a negative impact on that something  eating something has a negative impact on that something & some people eat slice -> animals have negative impact on cacti animals have negative impact on cacti  people have yes sweat on berry & if something has a negative impact on an organism then that organism must protect itself from that something -> a cactus must protect itself from animals a cactus must protect itself from animals  a cactus spine can be used as protection & a black optional protect itself from people -> a cactus spine is a part of a cactus for protecting the cactus from animals