Final answer:
In the sentence provided, the infinitive is 'to travel,' acting as a noun as the object of the verb 'like'.
Step-by-step explanation:
In this particular sentence, the infinitive "to travel" acts as a noun. It serves as the object of the verb "like," indicating what Jill and her aunt enjoy doing. The infinitive "to travel" functions as a noun because it is the direct object of the verb "like."
It's important to note that infinitives can have different functions in sentences depending on their role. For example:
1. As a noun: "To travel is Jill's favorite hobby."
2. As an adjective: "Jill has a desire to travel."
3. As an adverb: "Jill and her aunt went to the Hudson River to travel."
In summary, in the sentence "Jill and her aunt like to travel along the Hudson River," the infinitive "to travel" functions as a noun, serving as the object of the verb "like" to express what Jill and her aunt enjoy doing.