In terms of size comparison, how might a child with cystic fibrosis appear?

Children with cystic fibrosis often have difficulty gaining weight and may struggle with growth due to malabsorption of nutrients, lung complications, and the metabolic demands of fighting infections. This condition can lead to a body composition that is below the average height and weight for their age group. Consequently, these children may be described as small for their age since they may have lower body mass index (BMI) and may not meet the standard growth percentiles like their peers without the condition.

In contrast, the other choices reflect body compositions that are typically inconsistent with the diagnosis. Being obese or average size for their age would not usually align with the challenges that cystic fibrosis presents regarding nutrition and lung function. Additionally, tall and slender children might suggest a different set of health or nutritional habits that are not characteristic of the growth patterns seen in children with this condition. Thus, small for their age accurately captures the expected physical stature of a child affected by cystic fibrosis.