A VPC public subnet is one that:

A.
Has at least one route in its associated routing table that uses an Internet Gateway (IGW).

B.
Includes a route in its associated routing table via a Network Address Translation (NAT) instance.

C.
Has a Network Access Control List (NACL) permitting outbound traffic to 0.0.0.0/0.

D.
Has the Public Subnet option selected in its configuration.

Explanation: