The question asks to identify theories related to fertility from the given options.

Fertility Theory Explanations

• Social capillarity theory: This theory suggests that as societies modernize and social mobility increases (like rising up a capillary tube), people tend to have fewer children. This is linked to aspirations for upward mobility and changing social norms, impacting fertility rates.
• Social Network Theory: Social networks influence individual behavior, including fertility decisions. Norms, peer pressure, information sharing, and social support within networks can shape choices about family size and timing.
• Wealth flow theory: This theory focuses on the economic calculus of having children. It posits that fertility behavior is influenced by the perceived net flow of wealth between parents and children. High fertility is often associated with situations where children represent an economic asset (wealth flowing to parents), while low fertility occurs when children are perceived as economic costs (wealth flowing from parents to children).
• Change and response theory: While broader demographic theories address change and response, this specific phrasing isn't a standard, distinct theory primarily focused on explaining fertility patterns like the others listed.

Identifying Relevant Theories

Based on the explanations:

• Social capillarity theory directly relates to changing fertility patterns during modernization.
• Social Network Theory influences fertility decisions through social mechanisms.
• Wealth flow theory is a core theory explaining variations in fertility levels based on economic intergenerational transfers.

Therefore, theories A, B, and C are directly related to fertility.

Conclusion

The correct option includes Social capillarity theory, Social Network Theory, and Wealth flow theory.

Selected Option: A, B, C Only