Final answer:
The interjection in the sentence 'A dinosaur ate him. Yuck!' is 'Yuck!'. Interjections are words or phrases that express strong emotions or sudden bursts of feeling. They are often used to convey surprise, disgust, joy, or other intense emotions.
Step-by-step explanation:
The interjection in the sentence 'A dinosaur ate him. Yuck!' is 'Yuck!'. Interjections are words or phrases that express strong emotions or sudden bursts of feeling. They are often used to convey surprise, disgust, joy, or other intense emotions. In this case, 'Yuck!' expresses disgust at the idea of a dinosaur eating someone.