What do we know about gender gap from the study
A. It exists only in one’s 20s and 30s when people are in the critical period of career development.
B. It causes the great difference for people’s earnings in their 20s and 30s.
C. It is the greatest in parents’ best years of bearing and rearing children.
D. It helps fathers get good excuses when they don’t want to look after the children.