What Is the Most Likely Factor Involved in the Decreased

What is the most likely factor involved in the decreased birth interval seen in sedentary !Kung communities,as compared to more nomadic groups?

A) changes in infant feeding practices that result in a faster return of fertility
B) a shift away from the post-partum sex taboo seen in more nomadic groups
C) a more diverse diet resulting in greater nutritional stores in the mother
D) a social preference for a bigger family in sedentary communities