The correct answer is option 'D', ULSI (Ultra Large Scale Integration).

Fifth Generation Computers, also known as Knowledge Information Processing Systems (KIPS), were developed in the late 1980s and early 1990s. These computers were characterized by their advanced capabilities, including natural language processing, parallel processing, and artificial intelligence.

The electronic components used in Fifth Generation Computers were:

1. Transistors:
- Transistors are the basic building blocks of electronic circuits.
- They act as switches or amplifiers in electronic devices.
- They control the flow of current in a circuit.
- Transistors were used in previous generations of computers as well.

2. Integrated Circuits (ICs):
- Integrated circuits are miniaturized electronic circuits that contain many transistors, resistors, and capacitors on a single chip.
- They were a significant advancement over discrete transistors because they reduced the size, cost, and power consumption of electronic devices.
- Integrated circuits were widely used in previous generations of computers.

3. VLSI (Very Large Scale Integration):
- VLSI refers to the technology of integrating thousands or millions of electronic components onto a single chip.
- It allows for the creation of complex and powerful electronic systems in a compact form factor.
- VLSI was a major breakthrough in the development of Fifth Generation Computers, as it enabled the integration of massive computing power and memory into a single device.

4. ULSI (Ultra Large Scale Integration):
- ULSI takes VLSI technology to the next level by integrating billions of electronic components onto a single chip.
- ULSI allows for even greater computing power, higher storage capacities, and more advanced functionalities.
- ULSI was the key technology used in Fifth Generation Computers to achieve the advanced capabilities required for knowledge processing, parallel processing, and artificial intelligence.

In summary, while transistors and integrated circuits were used in previous generations of computers, it was the development of VLSI and ULSI technologies that enabled the creation of Fifth Generation Computers with their advanced capabilities. ULSI, in particular, played a crucial role in integrating massive computing power and memory onto a single chip, making Fifth Generation Computers possible.