0ne of them is alone. 其中一头落单了
0ne will have to do. 总有一只难逃噩运
0ne and a half billion swarm across the savannahs of Africa. 以15亿的数量聚集在非洲的稀树大草原上
0ne out of every two cubs do not survive their first year out on the ice. 两只幼熊中往往会有一只无法在第一年存活下来