Explanation:

FORTRAN (Formula Translation) was one of the earliest high-level programming languages, developed by IBM in the mid-1950s. Its widespread adoption and use began in the Second Generation of computers (approximately 1959-1965), which were characterized by transistors replacing vacuum tubes. This generation saw the shift from machine and assembly languages to more user-friendly high-level languages like FORTRAN and COBOL. The (a) First generation primarily used machine language. The (c) Third and (d) Fourth generations continued to use and develop high-level languages but FORTRAN's prominence began in the second. Therefore, the Second generation ($ \text{b} $) is when FORTRAN became a significant programming tool.