What kind of document serves as a legally binding contract or part of a contract that defines, in plain language and in measurable terms, the aspects of a service provided to a customer?

The answer is a service-level agreement.

Explanation:

A service-level agreement can be defined as a kind of engagement that exists between a service provider and a client. The aspects that are common to this engagement are established between the service provider and the user. These aspects include quality, availability, responsibilities.

The main element concerning a service-level agreement refers to the fact that the services must be furnish to the customer according to the different aspects established in the contract. An example of this could be Internet service providers that include some service level agreements according to the terms that were established with the customer in the contract.    

answer: fact: italy has over 300 islands ranging from extremely small uninhabited islands to the huge island of sicily.

explanation:

opinion: italy has way to many islands

answer; the correct answer is (composition);