英文70年代早期怎么说? 书上有 in early 1970s 和 in early 1970s ,哪个对?不懂的不要说

In the early 1800's 译文：在19世纪早期. 年代的翻译是怎么界定的? In the early 1800's 译文：在19世纪早期.年代的翻译是怎么界定的? in early 1990s还是in the early 1900s? in his early 30's 用英文如何表示世纪用英文说世纪是有两种方法吗?例如,in the early 1900s 和 i the early 2 in the early 1990s和in the early 2000s分别是指多少年啊? in,on,at early morning哪个对? 英语翻译In the early 1970s,he succeeded in developing the world’ in one's early twenties和in one's late twenties意思是一样的吗?为什么一个是 in her early 30s 与 in her early 30‘s in one"s early twenties 与 in one"s late twenties 有什么区别?（one" in the 1970s；in 1970s；in 1970's；in the 1970's哪个对?