Final answer:
The Internet Gateway Service is used to provide outgoing only internet access to an IPv6 instance by facilitating connectivity from the instance to the internet. option 1 is correct.
Step-by-step explanation:
The service used to provide outgoing only internet access to an IPv6 instance is typically known as an Internet Gateway Service.
This service facilitates the connectivity from the instance within a private network to the internet, allowing the instance to send traffic out to the internet while preventing unwanted inbound traffic. It's important to note that an Internet Gateway does not restrict outbound traffic, allowing instances to initiate communication with external hosts.