When incorporating direct quotations into writing, what is the function of parentheses?

The correct answer is that the function of parentheses when it comes to direct quotations is to add words that are not included in the direct quotation. So, for example, if you want to quote someone, but the quote is kind of out of context, then you need the brackets to add a word in order to make everything make sense.

Explanation:

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."

the krebs cycle and electron transport occur in the mitochondria, though other than that i would need to know more information.