Concept:Tall parents can have a short child only if both parents carry a recessive gene for shortness.Explanation:Let tall allele be T and short allele be t.Shortness is recessive, so a short child has genotype tt.For a child to be tt, both parents must contribute a t allele.Therefore, each tall parent must be heterozygous, Tt, carrying the gene for shortness.Answer: A. both parent possess genes for shortness