Plastic rings that are also used to hold some notebooks together come from petroleum.塑料环是来源于石油的,也是用于订装组合一些笔记本。Today, many fish are caught before they are old enough to reproduce.今天,许多鱼在足够成熟而得以繁殖之前就被捕获。For example, elephants give birth to a calf once every four or five years.例如,大象每隔四、五年才生一头小象。Overhunting is also blamed for the extinction of giant lemurs in Madagascar, moas in New Zealand, and giant kangaroos in Australia, among many other animals are also threatened by overhunting because some people think that the money obtained from animal skins is worth the danger.过度猎杀也造成了马达加斯加大狐猴、新西兰大鸟和澳大利亚巨型袋鼠的灭绝。 许多其他的动物也被过度猎杀所威胁,因为有些人认为从兽皮中获取金钱值得冒险。Renewable resources are those that can be replaced by a natural process given enough time. 可再生资源是那些能够通过一个给予充分时间的自然过程而被取而代之的。