Answer: "To give is one of the best things people can do. Volunteering their time shows what caring people they are".
Explanation: A gerund is a non-finite verb form that ends in -ing and functions as a noun. An infinitive is also a non-finite verb form, but it is formed with "to" and the simple form of a verb. Moreover, an infinitive can work as a noun, an adjective or an adverb. In the passage provided, "giving" is a gerund because it ends in "-ing" and it is working as a noun; therefore, it must be transformed into an infinitive by adding "to" and writing the simple form of the verb: "give". Furthermore, "to volunteer" is an infinitive because it is made up of "to" and the simple form "volunteer". "To volunteer" must be changed into a gerund by deleting the "to" and converting "volunteer" into a gerund: "volunteering".