Use the article a, an, the
put x if there's no article needed

The answer should be either "or a circle." OR "or the circle."

Explanation; A good rule of thumb to use when deciding to use "a, an, the" is to read the sentence out loud with each article and you can usually rule out one or more of the answer choices because the wrong ones will not sound right if you say it out loud

because of all the immigration, america became one big melting pot. the diversity of cultures from all over the world made america somewhat divided as well. people that immigrated stayed with their kind, and their traditions, while native born americans stayed with their kind and their traditions. normally, people born in american scorned the immigrants as well. the new religions also divided america. in summary, it took away from the american culture and identified america as the "melting pot."