With respect to the WBS numbering system, which of the following statements is true? A. The numbering system is a unique identifier known as the code of accounts, which is used to track the costs of the WBS elements. B. The numbering system is a unique identifier known as the code of accounts, which is used to track time and resource assignments for individual work elements. C. The numbering system is a unique identifier known as the WBS dictionary, which is used to assign quality control codes to the individual work elements. D. The numbering system is a unique identifier known as the WBS dictionary, which is used to track the descriptions of individual work elements.