You have servers in your private subnet in a VPC which need to access the Internet.
How could you achieve this?
The solution needs to be highly available.

Answer options:

A.Convert the subnet to a public subnet
B.Deploy a NAT instance
C.Deploy a bastion host
D.Use the NAT gateway service

Answer D
Since a highly available solution is required , it is advisable to use the NAT gateway option
For more information on the differences between the NAT instance and the NAT gateway please see the below link:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-nat-comparison.html