<em>The pair of words that is made up of synonyms is</em><em> C. assent/consent.</em>
Explanation:
A <u>synonym</u> is a word or phrase that means exactly, or at least nearly the same as another in the same language in some or many senses. Within these options, the pair that is made up of synonyms is C because <em>to assent </em>means to approve of something or to agree, and<em> to consent</em> means to give approval or assent, so they share the same meaning in that sense.