Which of the following logic families has the highest packing density?

The correct answer is option 2):(MOS)

Concept:

Metal Oxide Semiconductor (MOS) logic is most used  due to lower power consumption, small sized transistor, and high transistor density.

Metal Oxide Semiconductor Logic: Suitable for systems with high component density.

MOS logic family has higher packing density.

Additional Information​

• Transistor-Transistor Logic: Standard logic family; used for the longest time. It consume more power
• Emitter Coupled Logic: Suitable for systems requiring high-speed operations.
• Complementary Metal Oxide Semiconductor Logic: Suitable for systems with low power consumption (VLSI circuits). Gradually becomes the dominant logic family.