英语一些语法问题
1,ing,ed怎么区分
比如 a.The remainder was produced from natural gas,hydro power(each producing 20 units) and oil(which produced only 10 units).
括号里怎么前者用ing,后用ed呢?
b.By 2000 nuclear power had developed into the main source,producing almost 75% of electricty,while coal and oil together produced only 50 units.
和上面同样的问题,producing 和 produced
2,c.By 2000 these two countries relied on different principal fuel sources.
bye 2000后面不是应该加完成时吗,为什么用的relied on 而不是 had rely on