About the computer generation in which transistors were introduced.

The question asks about the computer generation in which transistors were introduced.

• First Generation (1940s-1950s): Used vacuum tubes.
• Second Generation (1950s-1960s): Used transistors.
• Third Generation (1960s-1970s): Used integrated circuits (ICs).
• Fourth Generation (1970s-present): Used microprocessors.

Based on the characteristics, transistors were introduced in the second generation of computers.

The final answer is $\text{B. Second}$.