Final answer:
In codominance, when a solid-colored cow (CC) is crossed with a spotted cow (SS), all offspring will display both solid color and spots. The correct answer is option 4.
Step-by-step explanation:
When a solid-colored cow with genotype CC is crossed with a spotted cow with genotype SS and the alleles are codominant, all the offspring will have a mixture of spots and solid colors. This is because the offspring will have one allele from each parent (CS), expressing both the solid and the spotted traits simultaneously.
In general, codominance is a form of inheritance wherein both alleles in a heterozygote are fully expressed, leading to offspring with a phenotype that is neither dominant nor recessive but a combination of both parental traits. This is different from incomplete dominance, where the phenotype is an intermediate blend of the parental traits, or complete dominance where only one trait is visibly expressed in the heterozygote.