The correct answer is parentheses.
When you are quoting somebody's words, first you are going to use the quotation marks ("), then cite the quotation, write a period, and close the quotation with the marks again. In order to avoid plagiarism, you have to cite your sources. This means that you need to use the parentheses, where you are going to write where you took that citation from.
For example:
<em>What characterizes romantic poetry is the "spontaneous overflow of powerful feelings" (Wordsworth 263).</em>
As you can see, the source (Wordsworth) is written in the parentheses, along with the page number.
