in 1950s 与in the 1950s有什么区别?in 1950s是表示1950----1959还是1940---1949?in the 1950s呢?

in the 1960's 与 in the 1960s 区别 in 1950s 与in the 1950s有什么区别?in 1950s是表示1950----1959还是1940---1949?in the 1950s呢? in 1980's 与 in the 1980's的区别 In the 90s 与In 90s 的区别 in the barber与in the barber's用法区别 in the 1980s 与 in 1980的区别 in the 1950s 还是in 1950sin the 1950's 还是 in 1950's in the 1950s还是in 1950s 英译中 in the 1950s in the 19th century in the cat,s In the stationary’s in the 1940s 与in the 1940's的区别?为什么My brother served in the army in the 1940's.这一句子中要用in the 1940‘s而不用in the 1940s? in the 1980s与in the 1980's一样吗 in the 1660s与in the 1660‘s的区别 in the in the 1720's呢? in the 1970与 in the 1970s 有什么区别吗?in the 1970 与 in the 1970s 有什么区别吗? in 1950 ,in 1950s,in the 1950s,in the 1950's,in 1950's这四个短语都存在么? in 1980/in 1980s / in the 1980 / in the 1980s / in the 1980's/in the 1980'