The correct answer is B) 8 to 12 days. When the body's water content is carefully preserved by avoiding perspiration, the average person can typically survive 8 to 12 days without any additional water intake. This is because the body can conserve and recycle water internally to maintain basic functions, as long as no significant water loss occurs through sweating or other means. The other answer choices are incorrect, as 3 days is too short, and 15-30 days would exceed the typical survival window under these conditions.