Voicemail Pro on Server Edition supports up to 150 simultaneous channels (Option C), allowing extensive voicemail and auto-attendant capacity. This requires sufficient licensing and server resources. Options A, B, and D represent lower or higher limits not aligned with Server Edition specs.References: Avaya IP Office Voicemail Pro Administration Guide.

IP Office supports up to 128 simultaneous conference channels (Option B), allowing multiple conference calls with a total of 128 participants across all conferences. This requires sufficient hardware and licensing.
Options A, C, and D exceed or fall short of this limit.References: Avaya IP Office Conference Configuration Guide.

The one-X Portal is a web-based application providing call control, IM, and presence. It is enabled by multiple user profiles: Option A (Office Worker), Option B (Power User), and Option C (Teleworker), depending on the user's role, making Option D ("All of the above") correct. Each profile includes one-X Portal access with varying additional features.References: Avaya IP Office one-X Portal User Guide, Licensing Guide.