This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Significant weight loss is defined as: 
Select and explain. 
A. 5% weight loss in 1-2 months, B. 5% weight loss in 2-3 months, C. 10% weight loss in 1-2 months, D. 10% weight loss in 2-3 months
A: 5% weight loss in 1-2 months
Answer: A: 5% weight loss in 1-2 months 
Explanation: Answer is A (5% weight loss in 1-2 months): Significant weight loss is defined as 5% weight loss in I month. Percent weight change over a period of time is calculated using the person's current body weight and person's usual body weight. Usual weight -- Current weight Percent weight change = Usual weight