The device that can act as a complete electronic circuit is

Junction diode

Integrated circuit

Junction transistor

Zener diode

Answer

Integrated circuit

Integrated circuits are miniature electronic circuits produced within a single crystal of semiconductors such as silicon. They contain a million or so transistors and resistors or capacitors. They are widely used in memory circuits, microcomputers, pocket calculators and electronic watches on account of their low cost and bulk, reliability into specific regions of the semiconductor crystals.