Question

a study led by scientist rebecca kirby at the university of wisconsin - madison found that black bears that eat human food before hibernation have increased levels of a rare carbon isotope, ______ due to the higher c levels in corn and cane sugar. bears with these elevated levels were also found to have much shorter hibernation periods on average. which choice completes the text so that it conforms to the conventions of standard english?
carbon - 13 ( c)
carbon - 13, ( c)
carbon - 13 ( c)
carbon - 13, ( c).

Explanation:

In Standard English, when an abbreviation is used after a full - name term, the comma should be outside the parentheses. Also, the sentence should end with the appropriate punctuation. Here, the text before the blank is a complete thought, and the information in parentheses is additional. The correct punctuation to end the non - parenthetical part is a comma, and the parentheses are part of the appositive for "a rare carbon isotope".

Answer:

carbon-13 (C),