Final answer:
In the inheritance of flower color in four-o'clock flowers with incomplete dominance, crossing purebred white (WW) flowers with purebred red (RR) flowers produces all offspring with pink color (RW), as both alleles are expressed and neither is completely dominant.
Step-by-step explanation:
When discussing the four-o'clock flowers and their inheritance of flower color, we are dealing with a phenomenon known as incomplete dominance. In this scenario, purebred white flowers with the genotype WW are crossed with purebred red flowers with the genotype RR, and according to the principles of incomplete dominance, the resulting progeny will all have the genotype RW and express a pink color. This pink color is intermediate between the red and white parent flowers, indicating that neither allele is completely dominant over the other.
To determine the offspring genotype, a Punnett square can be used. Both parents contribute one allele to their offspring, so when we cross WW (white) with RR (red), all the offspring will have the genotype RW and display pink flowers since red and white alleles are incompletely dominant.
Therefore, the correct answer to the question is: a) all pink flowers (RW). This is because the offspring will have one allele for red and one allele for white, resulting in the intermediate pink phenotype.