They were both presidents
The correct answer is a) caste.
In India, the division of kin groups in Jatis is not based on a specific principle, varying from ethnic origins to geographical occupation, exhibiting some variance. While the Jatis have not presented a fixed hierarchy, they present notions of a rank achieved over time considering lifestyle and social, political or economic status and considering the fact that the caste has a direct impact in these factors, we understand why it is the more relevant idea.
The correct answer is D.) Court clerks refusing to issue marriage licenses to same-sex couples.
The definition of grassroots activism is a movement that is born out of the personal convictions of an individual or a group of individuals about a particular issue and that is not originated in the will of an established political movement or leader (s). It is considered that a grassroots movement is spontaneously created by the will of ordinary citizens who want to make their voices hear about a particular issue and although its later stages may involve participation of political groups or leaders, the initiative for its inception was the concerns of ordinary citizens. This answer is a direct reference to the case of Sandra Davis, a Kentucky country Clerk that refused to issue same-sex marriage licenses due to her own personal convictions and in the name of "religious liberty". Her initiative was purely personal and was not the result of organized political efforts.