The correct answer is C. Vacuum tube based.
First generation computers were based on vacuum tubes, which are large, bulky, and consume a lot of power. They were also very slow, with speeds measured in kilohertz. However, they were a major breakthrough at the time, and they allowed for the development of many new technologies, such as radar and nuclear weapons.
Transistors were invented in 1947, and they quickly replaced vacuum tubes in computers. Transistors are much smaller and faster than vacuum tubes, and they consume much less power. This allowed for the development of smaller, faster, and more efficient computers.
Integrated circuits were invented in 1958, and they further miniaturized computers. Integrated circuits are made up of thousands or even millions of transistors that are etched onto a single piece of silicon. This allowed for the development of even smaller, faster, and more efficient computers.
VLSI microprocessors were invented in the early 1970s, and they revolutionized the computer industry. VLSI microprocessors are made up of millions or even billions of transistors that are etched onto a single piece of silicon. This allowed for the development of personal computers, which are now ubiquitous in our society.
In conclusion, the base of first generation computer systems was vacuum tubes. Vacuum tubes were large, bulky, and consumed a lot of power, but they were a major breakthrough at the time, and they allowed for the development of many new technologies.