Which the following type of authentication on Mobile Access can NOT be used as the first authentication method?

Dynamic ID generates a one-time password that must be delivered to a user who has already been partially identified, making it inherently a second-factor mechanism. Check Point Mobile Access requires the first authentication method to independently verify identity, which OTP alone cannot do. Therefore Dynamic ID is restricted to use as a subsequent factor only.

RADIUS is a supported first authentication method in Mobile Access because it can independently verify credentials against a RADIUS server.

Username and Password is the most common first authentication method and is fully supported as an initial factor in Mobile Access.

Certificate-based authentication is a valid first authentication method because the certificate itself establishes user identity without requiring a prior step.