Which of the following ICs has lowest power consumption?

Explanation

ECL (Emitter Coupled Logic) has the highest power consumption among standard logic families because its transistors are kept in the active, non-saturated region for high switching speed, and TTL also dissipates significant power through its resistor-transistor conduction paths. MOS logic draws less power than these bipolar families, but CMOS consumes the least because in a CMOS gate only one of the complementary pull-up/pull-down transistor networks conducts at a time, so almost no static current flows except briefly during switching. Hence CMOS has the lowest power consumption of the four.