The single-rate method does not discriminate between fixed and variable costs. It allocates costs in each cost pool to cost objects using a single charging rate. In contrast, the dual-rate method divides the cost of each support department into two separate pools, variable and fixed. It distributes the cost of each pool by using a different charging rate. When using either the single-rate method or the dual-rate method, managers can allocate support-department costs to operating divisions based on either a budgeted rate or the eventual actual cost rate (Datar and Rajan, 2018: 622). 

The correct answer is A.