６．og 2０４ in recent years cattle breeders have increasingly used crossbreeding , inpart that their steers should acquire certain characteristics and partly their steers should acquire crossbreeding is said to provide hybrid vigor. b)in part for the acquisition of certain characteristics in their steers c)partly because of their steers acquiring certain characteristics d)partly because certain characteristics should be acquired by their steers e)partly to acquire certain characteristics in their steers(best answer) 到底steer 这里扮演什么角色啊？？ | 
