Which of the following is the first step to prevent unauthorized access on a lost mobile device?

While enabling two-factor authentication adds an extra layer of security for accounts accessed from the device, it does not prevent immediate unauthorized access to the device itself. If the device is lost, an intruder can bypass account protections until they access the device, which makes this step less effective as a first measure.

Setting up a remote wipe is a useful security feature that allows users to delete data from a lost device; however, it requires the device to be accessible first. If the device is already lost, configuring a screen lock is more immediately effective in preventing access until a remote wipe can be executed.

Geofencing is a feature that can provide alerts when a device moves outside a predefined area but does not inherently prevent unauthorized access. If the device is lost, this feature does not secure the information on the device or block access until it is recovered.