Communication systems — match each service to its typical modulation/format List I (Service) A. Television (legacy analog systems) B. Radio broadcasting (AM/FM broadcast) C. Radar D. Data communication List II (Characteristic) 1. Either AM or FM used 2. Both AM and FM are used in the system 3. PCM is used 4. Digital system

Introduction / Context:
Different services historically adopted different modulation formats. Recognizing conventional (legacy) pairings aids in interpreting block diagrams and spectrum allocations, even as modern systems migrate to fully digital methods.

Given Data / Assumptions:

• Television (analog): video commonly AM (vestigial sideband), audio FM → “both AM and FM are used.”
• Radio broadcasting: stations use either AM (MW/LW) or FM (VHF) → “either AM or FM used.”
• Radar: pulse coding and telemetry often employ PCM in control/recording channels (not the RF carrier modulation itself), aligning with the list statement.
• Data communication: broadly a digital system (PCM/line coding/packetization).

Concept / Approach:
Map each service to the list item that encapsulates its typical legacy or supporting modulation/format. While modern TV and radio may be fully digital (DVB/HD Radio), the list aligns with canonical textbook descriptions.

Step-by-Step Solution:

Verification / Alternative check:
Analog TV standards (NTSC/PAL/SECAM) and broadcast engineering texts affirm the AM+FM combination; broadcast radio uses distinct AM and FM bands; radar documentation describes PCM in data channels.

Why Other Options Are Wrong:

• Assignments that swap radio and TV ignore the AM/FM split versus combination.
• Mapping data communication to “both AM and FM” mischaracterizes digital networking.

Common Pitfalls:
Assuming all modern services are strictly digital; the question references conventional pairings used in classic curricula.

Final Answer:
A-2, B-1, C-3, D-4