Incomplete dominance is the phenomenon of none of the alleles being dominant, with the effect that the hybrid produced by crossing two pure individuals is a mixture between the parents.

Explanation:

When a red (RR) Antirrhinum is crossed with a white (WW) one, the resulting offspring are pink (RW). This is an example of incomplete dominance.

Incomplete dominance occurs when the heterozygous phenotype is intermediate between the two homozygous phenotypes. In this case, the pink color of the offspring is a blend of the red and white colors of the parents.

Key Points:

- Incomplete dominance: When the heterozygous phenotype is intermediate between the two homozygous phenotypes.
- Red (RR) Antirrhinum crossed with white (WW) results in pink (RW) offspring.
- Pink color is a blend of the red and white colors of the parents.

Comparison with Other Options:

a) Dominant - recessive: In dominant-recessive inheritance, one allele is dominant and masks the expression of the recessive allele. This is not the case in the given scenario, as neither the red nor the white allele is dominant over the other.

c) Hybrid: Hybrid refers to the offspring resulting from the cross between two different species, varieties, or breeds. In this case, both the red and white Antirrhinum are of the same species, so the term hybrid is not applicable.

d) Supplementary genes: Supplementary genes refer to genes that interact with one another to produce a specific phenotype. This is not the case in the given scenario, as the pink color is a result of incomplete dominance rather than the interaction of supplementary genes.

Conclusion:

The given scenario of a cross between a red (RR) Antirrhinum and a white (WW) one, resulting in pink (RW) offspring, is an example of incomplete dominance. The pink color of the offspring is a blend of the red and white colors of the parents.