The author mentions all of the following as causes...

C

- Hướng dẫn giải

Phương pháp giải:

Giải chi tiết:

C

Thông tin ở đoạn 2:

- rising living standards were cutting down the size of families. (better standards of living)

- young married couples were buying automobiles or houses before starting families (couples buying houses)

- Young people were staying at school longer (people being better educated)