What is the fundamental principle behind the "Standard Price" costing method when used for product valuation?  
A) Management sets a fixed, predetermined cost that remains unchanged until further notice.

B) Inventory valuation is determined by the average cost of all items over a specified period.

C) The cost is affected by the assumption that the first units purchased are also the first units sold.

D) It tracks and analyzes the precise purchase price of each individual item to evaluate its value.