質問: against under what system had black people in south africa been discriminated against? という質問で、 they had been discriminated under a system called apartheid. と答えたのですが、正答は they had been discriminated against under the system called apartheid. でした。 なぜagainst が入るのでしょうか。また、a system よりthe system の方が良いのでしょうか。よろしくお願いします。
回答: ありがとうございます!