Which VPC component provides a layer of security at the subnet level?

Explanations:

Security groups operate at the instance level, providing control over inbound and outbound traffic per instance.

Network ACLs (Access Control Lists) operate at the subnet level, providing a layer of security by allowing or denying traffic to and from entire subnets.

NAT gateways are used to enable instances in a private subnet to access the internet, not for subnet-level security.

Route tables are used to control traffic routing within a VPC, not for enforcing security at the subnet level.