If a ping to 10.0.100.19 is unreachable, the most likely issue is that users are on the wrong subnet and cannot communicate with the server.
Breakdown of Options:
A). The users are on the wrong subnet. # Correct answer. If users are on a different subnet without proper routing, they won ' t reach the server.
B). The DHCP server renewed the lease. - Would change the client's IP, but the server's static IP should remain unchanged.
C). The IP address was not reserved. - DHCP reservations matter for dynamic IPs, but RDP servers typically have static IPs.
D). The hostname was changed. - Would affect DNS resolution, but pinging the IP directly would still work.
Reference:
CompTIA Network+ (N10-009) Official Study Guide - Domain 2.4: Explain subnetting concepts.