Answer: C) The children enjoyed climbing on the playground equipment.
Step-by-step explanation: A gerund is a word that has the form of a verb, but it acts like a noun (it can be a subject or an object in a sentence). The structure of a gerund is the root of the verb, plus the ending "ing." From the given sentences, the one that is an example of a gerund is "The children enjoyed climbing on the playground equipment" because in this case "climbing" acts like a noun (and the direct object of the sentence).