The notions of complementarity, structuralism, and general systems theory are all embraced by which family theory?

Structural family therapy (SFT)

Explanation:

Structural family therapy (SFT) is defined as the treatment that is based on interaction structure and function which creates problems in families. Change in structure and pattern of family is basic treatment given in problematic conditions.This method does not consider focusing on individual change.

Structuring,considering traits  and characteristics of social relationship of family members and  understanding people's behavior instead of just changing interaction structure are the factors that are used by structural family therapy .

world bank is the correct answer.

i would say b. research typically uses a variety of sources