AWS Certified Solutions Architect - Professional (#505)

An organization is having a VPC for the HR department, and another VPC for the Admin department. The HR department requires access to all the instances running in the Admin VPC while the Admin department requires access to all the resources in the HR department. How can the organization setup this scenario?

Setup VPC peering between the VPCs of Admin and HR.
Setup ACL with both VPCs which will allow traffic from the CIDR of the other VPC.
Setup the security group with each VPC which allows traffic from the CIDR of another VPC.
It is not possible to connect resources of one VPC from another VPC.