Michel Foucault is very important in gender studies, sexuality studies, and cultural theory.
He studied the relationship between power, knowledge, discourse, and sexuality.
According to Foucault, sexual identities are not simply natural or fixed.
They are shaped through historical discourses, social institutions, power relations, and cultural practices.
So Assertion (A) is correct.
Reason (R) is also correct because it explains Foucault's idea that sexual identities are constructed through discourse and power.
Since this directly explains why gender studies are indebted to Foucault, Reason (R) is the correct explanation of Assertion (A).
Therefore, the correct answer is option (A).