Correct Answer: C

Rationale: The correct answer is C: Absence of parasympathetic ganglion cells in a portion of the colon. Hirschsprung disease is a congenital condition characterized by the absence of nerve cells (ganglia) in parts of the colon. This absence leads to a lack of peristalsis in the affected segment, resulting in severe constipation and bowel obstruction. Choices A, B, and D are incorrect. Choice A describes symptoms of diarrhea rather than a causative factor of Hirschsprung disease. Excessive peristaltic movement (choice B) is not a causative factor but rather the opposite, as Hirschsprung disease is associated with reduced peristalsis. Choice D, which refers to intussusception, is a different condition unrelated to Hirschsprung disease.

Correct Answer: A

Rationale: The correct answer is fats. Fats provide 9 kilocalories per gram, which is more energy-dense compared to proteins and carbohydrates. While proteins and carbohydrates provide 4 kilocalories per gram, fats provide more than twice the energy, making them the most energy-providing nutrient. Alcohols are not considered essential nutrients and do not provide energy for the body, unlike fats, proteins, and carbohydrates. Therefore, fats are the correct answer for the most energy-providing nutrient.

Correct Answer: C

Rationale: There are 16 essential minerals required for human nutrition. These minerals include calcium, potassium, iron, and others. Choice A (8) is incorrect as it underestimates the number of essential minerals. Choice B (12) is also incorrect as it does not encompass the full count of essential minerals. Choice D (20) is incorrect as it overestimates the number of essential minerals.

Correct Answer: C

Rationale: In the scientific method, a hypothesis is a tentative solution or educated guess that is tested through research. A theory (choice A) is a well-substantiated explanation based on evidence and extensive testing. A prediction (choice B) is a statement about what will happen in the future based on existing knowledge. Correlation (choice D) refers to a mutual relationship between two or more things, indicating how they may change together but not providing a solution to a problem.

Correct Answer: D

Rationale: The correct approach in a scientific experiment is to prevent yourself from knowing the contents of the pill bottles and distribute them randomly to the subjects. This randomization helps to avoid bias and ensures that the results are not influenced by preconceived notions. Option A is incorrect because it introduces gender bias by assigning pills based on gender. Option B is incorrect as it mentions telling the subjects what they are getting, which could lead to placebo effects. Option C is incorrect as it suggests disclosing group information to the subjects, which can also introduce bias.