Final answer:
Amazon DevPay is the service that businesses use to sell applications built on the AWS cloud, making billing and account management seamless. Thus, option 3) Amazon DevPay is the correct answer.
Step-by-step explanation:
The billing and account management service businesses can use to sell applications they have built on the AWS cloud is Amazon DevPay.
Amazon DevPay is a service that simplifies the billing and account management of applications by integrating with Amazon Web Services.
Businesses can set prices for their applications and leverage AWS infrastructure to manage accounts and process payments, thus offering a convenient way for developers to charge for their cloud-based applications.
So, the correct answer is option 3) Amazon DevPay.