In grammar, the direct object is usually the word that appears after the main verb of a sentence and responds to the question "What?", this means, the direct object identifies the object that acts as a recipient of the action. For example, in the sentence "I bought a car" the direct object is "a car" as this is the recipient of the action of what was bough. Therefore, in the sentence "Most fish enjoy a lunch or dinner of worms" in which the main verb is "enjoy" the direct object is "a lunch or dinner" as this answers to the question "What does most fish enjoy?" and thus, "lunch,dinner" is the correct answer.
