after two decades of a baby boom,china made it a practice in the early 1970s.
问题描述：
after two decades of a baby boom,china made it a practice in the early 1970s.
1.baby boom
2.made it a practice
3.in the early
答
1.生育高峰
2.让它付诸实施.
3.在二十世纪七十年代早期