Which personal pronoun agrees with its antecedent and correctly completes the sentence?

"today's the day we're going to win! " cried susie. "no one can beat today! "

a.) we

b.) us

c.) they

the african society basically suffered the consequences of colonization and apartheid directly attacking the black people, first, during the colonialism and its main idea which which "white people" had better rights, affecting   them principally in the right to establish black people in their territories, access to quality education and health services and took away any civil right even to the black people to feel they have the same opportunities as the settlers.

what does the teacher mean