If only the dominant trait appears in Mendel's first generation, what is the correct conclusion about the recessive trait?

Correct answer: It may be hidden rather than absent.

Mendel’s principle of dominance explains why a dominant phenotype can mask a recessive one in the first filial generation. For example, an F1 plant with genotype Tt shows the dominant tall form, while the recessive allele t is still present in its genetic makeup. When alleles separate during gamete formation and combine again, the recessive phenotype can reappear in F2. Thus option A is correct; invisibility does not mean destruction or absence.