Using encryption is the best method to safeguard sensitive customer data during transit over an untrusted network like the public internet. It protects the confidentiality of the data by making it unreadable to unauthorized parties and maintains integrity by ensuring that any tampering would be detectable. Using a VPN adds a layer of security, but its primary answer assumes that the VPN is configured to use encryption, which is why it is not the direct answer. Physical controls are irrelevant for data in transit over the internet, and secure disposal applies to the end of the data's life cycle, not while it's in transit.