in the 1980s和in the 1980's是不是都对的?

in the 1980s和in the 1980's是不是都对的? in the 1980s,in the 1980's和in 1980s的区别 in 1900s 和 in the 1900s那个对? in 1980's 与 in the 1980's的区别 in the 19th 和in the 1980's what's in the box?和 what are there in the box?是否都对? 是in 1980s对还是in the 1980s对? in 1960's 和in the 1960s的区别 in the 1900s 和in 1900s的区别 in 1720s和in the 1720s的区别 in the 1970s；in 1970s；in 1970's；in the 1970's哪个对? in the 1920's和in the 1920s的用法都对吗,各自指的是什么年份