A Solutions Architect plans to migrate NAT instances to NAT gateway. The Architect has NAT instances with scripts to manage high availability.

What is the MOST efficient method to achieve similar high availability with NAT gateway?

A.

Remove source/destination check on NAT instances.

B. Launch a NAT gateway in each Availability Zone.

C. Use a mix of NAT instances and NAT gateway.

D. Add an ELB Application Load Balancer in front of NAT gateway.