The correct answer is: A. materials are purchased for specific job or work order.
The specific price method of valuing material issue is used when materials are purchased for a specific job or work order. This method is used to track the cost of materials used on each job or work order. The specific price method is also used when materials are subject to natural wastage. Natural wastage is the loss of materials that occurs during normal production processes. The specific price method is used to track the cost of materials that are lost due to natural wastage.
The other options are incorrect because they are not specific to the purchase of materials for a specific job or work order. Option B, materials are subject to natural wastage, is incorrect because natural wastage can occur regardless of whether materials are purchased for a specific job or work order. Option C, prices fluctuate, is incorrect because prices can fluctuate regardless of whether materials are purchased for a specific job or work order. Option D, None of these, is incorrect because one of the options is correct.