Correct Answer: C

Rationale: The correct answer is C, Down syndrome. Down syndrome is often associated with short stature and limited mobility, which can contribute to feeding difficulties and obesity. Parkinson's disease (choice A) primarily affects motor function, but it is not typically associated with short stature. Muscular dystrophy (choice B) primarily impacts muscle strength and does not necessarily lead to short stature. Multiple sclerosis (choice D) is a neurological condition affecting the central nervous system and does not directly cause short stature or feeding difficulties as seen in Down syndrome.

Correct Answer: C

Rationale: The correct answer is Vitamin B3, also known as Niacin. Niacin is essential for energy metabolism and can help improve cholesterol levels. Vitamin B1 is Thiamine, Vitamin B2 is Riboflavin, and Vitamin B12 is Cobalamin. These vitamins have different functions in the body and are not synonymous with Niacin.

Correct Answer: D

Rationale: Leg cramps are a common complication during hemodialysis due to shifts in fluid and electrolyte levels that occur during the treatment. Confusion (choice A) is not a common complication specifically related to hemodialysis. Profuse sweating (choice B) is not typically associated with hemodialysis complications. Hypertension (choice C) might be a pre-existing condition in some patients but is not a direct common complication of hemodialysis.

Correct Answer: C

Rationale: The correct answer is C, leptin. Leptin is a hormone produced by fat cells that helps regulate energy balance by suppressing hunger, thus aiding in the regulation of body fat. Glucagon (choice A) is a hormone that raises blood glucose levels, ghrelin (choice B) stimulates appetite, and insulin (choice D) regulates blood sugar levels and promotes glucose uptake.

Correct Answer: A

Rationale: The correct answer is A: Iron. Iron is an essential nutrient needed by the body to make hemoglobin, the protein in red blood cells that carries oxygen. While other nutrients like vitamin B12, niacin, and folate are important for various bodily functions, they are not directly involved in the production of hemoglobin. Vitamin B12 is essential for nerve function and DNA synthesis, niacin is important for metabolism, and folate is crucial for cell division and DNA synthesis. Therefore, only iron is specifically required for hemoglobin production.