Digital logic families — match each family to its hallmark characteristic List I (Logic family) A. TTL (Transistor–Transistor Logic) B. ECL (Emitter-Coupled Logic) C. MOS (PMOS/NMOS families) D. CMOS (Complementary MOS) List II (Trait) 1. Low propagation delay (very fast) 2. Low power consumption 3. High packing density 4. Saturated bipolar logic

Introduction / Context:
Comparing logic families is a staple of digital electronics. Each technology balances speed, power, and integration density differently. Recognizing these trade-offs guides family selection for timing-critical vs. low-power applications.

Given Data / Assumptions:

• TTL uses saturated bipolar transistors.
• ECL avoids saturation via emitter-coupled differential pairs.
• MOS (pre-CMOS) emphasizes integration density compared with bipolar.
• CMOS leverages complementary devices for very low static power.

Concept / Approach:
Map families to their hallmark: TTL → saturated bipolar (4); ECL → fastest, low propagation delay (1); MOS → high packing density (3); CMOS → low power consumption (2). While modern variants blur lines, the classical properties remain correct for fundamentals.

Step-by-Step Solution:

Verification / Alternative check:
Family datasheets and textbooks list typical t_pd and power numbers: ECL shows sub-nanosecond speeds at higher static power; CMOS shows nanojoule-level energy per transition and nearly zero static power.

Why Other Options Are Wrong:

• Swapping MOS and CMOS traits confuses density with static power advantages.
• Calling TTL “fastest” ignores ECL’s unsaturated design.

Common Pitfalls:
Assuming a single “best” family—real designs weigh speed, noise margins, and power together.

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