What is an example of an allusion.' a. The wind whipped like a rippling storm
b. She was as cold as ice
c. The mist rolled over the trees in the mountains

c. The mist rolled over the trees in the mountains.

Explanation:

An allusion is an expression that refers to another person or thing without making a direct reference to it. In other words, allusion is talking about something without directly referring to it.

Among the given sentences, sentence c is an allusion. It alludes to or refers to the mist as "rolling over" the trees. While the other two sentences are similes with their use of "as" and "like" in making the comparisons.

Thus, the correct answer is option c.