Answer : 3. "third generation"
Explanation :

Integrated circuits (ICs) were first introduced during the third generation of computers. The third generation of computers, which emerged in the 1960s, saw the development and widespread use of integrated circuits. These tiny electronic circuits contained multiple transistors, resistors, and capacitors on a single semiconductor chip. The use of integrated circuits significantly reduced the size of computers, increased their processing speed, and improved their reliability, marking a significant advancement in computer technology.