Identify parts of speech 

The correct word is "terrible" because "sounds" in this context acts as a linking verb. Linking verbs connect the subject of a sentence to a word or phrase that describes or identifies the subject.

Here's a breakdown:

• Linking Verbs: Verbs like be, seem, appear, feel, taste, smell, sound, look, grow, become, remain, stay are often linking verbs. They do not express an action performed by the subject but rather a state of being or a quality of the subject.
• Adjective vs. Adverb: When a linking verb is used, it should be followed by an adjective (like "terrible") to describe the subject (your cold), not an adverb (like "terribly") which would describe how the verb is performed.
• Example: "Your cold sounds terrible." Here, "terrible" describes the noun "cold" (or the state of the cold), not the manner in which the sound is made. If it were an action verb, an adverb would be appropriate (e.g., "The singer sang terribly").