A. Pool1 only Incorrect because it ignores the other host pools. If a user is assigned to a session host in Pool2, Pool3, or Pool4, they would still lack connectivity to App1.
B. Pool1 and Pool2 only Incorrect as it excludes the Windows Server-based host pools (Pool3 and Pool4). Connectivity requirements for on-premises apps apply to all OS types used in AVD.
C. Pool1 and Pool3 only Incorrect because it neglects Pool2 and Pool4. Partial configuration results in inconsistent user experiences depending on which host pool the user's session is routed to.
D. Pool1, Pool2, and Pool3 only Incorrect because it leaves out Pool4. To ensure comprehensive access across the environment, every pool's network path must be updated to recognize the new on-premises subnet.