Answer:
The very content cow chewed cud.
Step-by-step explanation:
An adverb is one of the eight parts of speech which is used to modify a noun, an adjective, and another adverb. The purpose of an adverb is to tell the reader about how, when, and where an action is performed or the quality/degree of an action.
From the given options, the sentence in which an adverb is modifying an adjective is the last one (fourth)
In the fourth statement, the adverb is informing about the degree (very) of adjective (content).
Thus option fourth is correct.