Final answer:
The punctuation mark used to insert words into a quotation is brackets. The correct answer is C Brackets.
Step-by-step explanation:
The punctuation mark used to insert words into a quotation, to help integrate source material into a sentence, is brackets (C).
When you alter a quotation to fit into your sentence, you must indicate the change you made. Brackets are used to indicate any changes or additions in a quotation. They are placed around the added or changed words and help to clearly indicate that those words were not in the original quotation.
For example, if the original quotation is: 'Cybersecurity is an important issue for businesses of all sizes. Every business from Fortune 500 companies to mom-and-pop stores has an obligation to protect customers' sensitive data.'
And you want to add information to make it more relevant to your sentence, you can use brackets like this: 'Cybersecurity is an important issue for businesses... Data breaches, such as the Target breach in 2014, have been known to erode [consumers'] trust [in the company].'