Final answer:
The sentence 'The clever nawion ate my pizza.' uses the nonsense word 'nawion' as a noun, as it serves as the subject of the sentence. The correct answer is option a.
Step-by-step explanation:
The student is asking which sentence uses the nonsense word 'nawion' as a noun. The correct sentence that uses 'nawion' as a noun is: The clever nawion ate my pizza.
The other sentences use 'nawion' as an adjective, which is incorrect based on this context. This is evident because in the other sentences 'nawion' is used to describe the cat, rather than acting as a standalone noun.