When requiring certificates for mobile devices, make sure the authentication method is set to one...

When requiring certificates for mobile devices, the authentication method should be set to one of the following:

Username and Password

RADIUS

SecurID (RSA SecurID)

So, the correct answer is option B, "SecurID."

Options A, C, and D are not standard authentication methods for mobile devices in this context.

References: Check Point Certified Security Expert (CCSE) R81 documentation and learning resources.