Wide Area Network (WAN) operation commonly uses which transmission facilities? Select the best overall choice.

Introduction / Context:
A Wide Area Network spans cities, countries, or continents. To cover such distances and diverse terrains, WANs rely on different carrier media and technologies—from terrestrial copper/fiber to microwave relays and satellite links. Recognizing the breadth of possible media clarifies why WAN design involves latency, availability, and cost trade-offs.

Given Data / Assumptions:

• WANs interconnect geographically distant sites.
• Media choices include wired and wireless carrier infrastructure.
• The question asks for the most inclusive correct choice.

Concept / Approach:
WANs may use public switched telephone networks, leased lines over copper/fiber, microwave line-of-sight backhaul, and satellite links (GEO, MEO, LEO). Modern WANs also overlay VPNs on the Internet and carrier Ethernet/MPLS backbones. Because multiple technologies are routinely used in combination, the correct answer aggregates these options.

Step-by-Step Solution:
Identify common WAN media: PSTN/leased lines, microwave, satellite.Acknowledge that many WANs mix these for redundancy or reach.Choose the inclusive option covering all.

Verification / Alternative check:
Real deployments often pair terrestrial fiber with microwave as backup and add satellite for remote/mining/oceanic locations where terrestrial build-out is impractical.

Why Other Options Are Wrong:
Single-medium choices (telephone, microwave, satellite) are incomplete.

None of the above: Incorrect because all listed media are valid WAN options.

Common Pitfalls:
Assuming WANs are always fiber only; last-mile and contingency links frequently use microwave or satellite where fiber is unavailable or cost-prohibitive.

Final Answer:
All of the above