Answer: A) some skiers think very highly of their sport.
Explanation: An action verb is a verb that expresses something that a person, animal, object, or process in nature can do, rather that what they are or seem to be. From the given options, the only one that contains an example of an action verb is the corresponding to option A: "some skiers think very highly of their sport" because the verb "think" is expressing an action, the verbs from the other options: "were," "appear," and "are" are expressing being.