A customer wants to make it convenient for their mobile workforce to access a CRM web interface that is hosted on Google Cloud Platform (GCP). The CRM can only be accessed by someone on the corporate network. The customer wants to make it available over the internet. Your team requires an authentication layer in front of the application that supports two-factor authentication Which GCP product should the customer implement to meet these requirements? 

Answer options:

A. Cloud Identity-Aware Proxy
B. Cloud Armor
C. Cloud Endpoints
D. Cloud VPN

D