Not Sure about...
C may be correct because of the firewall solution, but if he uses the Endpoint Protection suite, then harmony license is not required but a Endpoint license. Last are licensed based on all instead concurrent users. If harmony includes endpoint security than C should be the only right answer (see: https://www.checkpoint.com/downloads/products/harmony-solution-brief.pdf).
D could also be correct, if the mobile access solution for windows is used. There the concurrent user is the base for licensing. But the personal firewall is missing, that could be a checkpoint harmony or another vendor ;-)
So after reading and writing i would also say C...