<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 14-year-old boy is brought to the physician because of blurry vision. He is at the 97th percentile for height and 25th percentile for weight. He has long, slender fingers and toes that are hyperflexible. Examination of the oropharynx shows a high-arched palate. Slit lamp examination shows bilateral lens subluxation in the superotemporal direction. The patients older sister is also tall, has hyperflexible joints, and has hyperelastic skin. However, she does not have lens subluxation or an arched palate. Which of the following genetic principles accounts for the phenotypical differences seen in this pair of siblings?? A: Incomplete penetrance, B: Variable expressivity, C: Compound heterozygosity, D: Frameshift mutation, E: Chromosomal instability,  <response>: This is a question about genetic principles that explain phenotypic differences between siblings. The key information is that the siblings have some overlapping features like height, joint hyperflexibility and skin hyperelasticity, but also some distinct features like lens subluxation and arched palate seen only in the brother. The choices describe different genetic principles like incomplete penetrance, variable expressivity, compound heterozygosity etc. that can lead to phenotypic variations. To answer the question, we need to identify the principle that best explains the phenotypic overlap as well as distinct features between the siblings.B: Variable expressivity 