Rank the four technologies by how they draw current, and the numbers fall into place without memorising them.

b → iii. ECL — 25 to 73 mW, by far the highest. Emitter-coupled logic keeps its differential pair permanently conducting and never lets the transistors saturate. That constant bias current is what makes it the fastest bipolar family, and it is also why it burns the most power. Anything in the tens of milliwatts must be ECL.

d → i. Bipolar TTL (F) — 6 mW. TTL draws current whenever its output transistors conduct, so it sits in the milliwatt range — an order of magnitude below ECL but far above anything CMOS.

c → ii. CMOS (AHC) — 2.75 μW, the smallest. In a CMOS gate one of the two complementary transistors is always off, so in the steady state no d.c. path exists between supply and ground and only leakage flows. Static dissipation is in microwatts; the real power is dynamic,

\(P=\alpha C_LV_{DD}^{2}f\)

which is why CMOS power rises with clock frequency while ECL's does not.

a → iv. BiCMOS — 17 μW. BiCMOS uses CMOS for the logic and bipolar transistors only at the output, to drive heavy capacitive loads quickly. It therefore inherits CMOS's microwatt-level static power, but a little higher than pure CMOS because of the bipolar stages.

The ordering that settles the matching:

\(\text{CMOS} \lt \text{BiCMOS} \ll \text{TTL} \lt \text{ECL}\)

— 2.75 μW, 17 μW, 6 mW, 25–73 mW. Matching by magnitude alone gives the answer, and the pattern (microwatts for the two MOS-based families, milliwatts for the two bipolar ones) is the fact worth carrying away.

Hence, the correct matching is a-iv, b-iii, c-ii, d-i.