Final answer:
The answer is d) His best friend. Cassius associates 'Mustang' with his best friend.
Step-by-step explanation:
The answer to the question is d) His best friend.
In the context of the question, the word 'Mustang' is likely referring to a person. When Cassius sees or hears 'Mustang', it reminds him of his best friend. This suggests a strong emotional connection between the two.
For example, 'Mustang' could be the nickname of Cassius' best friend, or they could have shared a memorable experience related to a Mustang car. Regardless of the specific reason, Cassius associates 'Mustang' with his best friend.