in the 1970s；in 1970s；in 1970's；in the 1970's哪个对?

in the 1970s；in 1970s；in 1970's；in the 1970's哪个对? in the 1970s in 1970、in the 1970、in the 1970‘s、in the 1970s有什么区别 in 1970s; in the 1970's ; in the 1970s'.那种对呀, in the 1970s 的“s”表示什么? in the 1970s和in the 1970's有区别吗? in the 1970s和in the 1970's有区别吗,还有怎么读? in the cat,s Cat's in the in 1900s 和 in the 1900s那个对? in the 1970s和in 1970s 有什么区别 in the 1970s 世纪前要加the吗?