In any situation, you have a variety of pressures on an organism: what is the atmosphere, is there food available, what is the competition for resources?
在任何情况下，生物都有各种各样的生存压力，大气是什么样的，能否得到食物，资源的竞争是什么样的？
2
Like Barcelona, United have found themselves spoilt for choice up front this season and Rooney insisted that a variety of options and competition for places was only a good thing.