这个知识点老师上课讲过一遍,但我没有听明白。有一道题目就是根据这个出的。People _______ wore army uniforms and they all looked the same from the back.A.in the 1970s B.from the 1970s C.of the 1970s D.out of the 1970s老师告诉我们选A,但我想知道原因,A和B有什么区别,谢谢!