In a monohybrid cross, f2 refers to
a)the original mating pair
b)the grandparents of the 1st generation
c)the 1st filial generation
d)the second filial generation, or the "grandchildren" of the original mating pair

The answer is D) the second filial generation, or the "grandchildren" of the original mating pair.

In a monohybrid cross, the original mating pair is called a parental generation (P). The offspring of parental generation is the first filial generation (F1). The offspring of the first filial generation (and the "grandchildren" of the original mating pair) is called the second filial generation (F2).