Answer: Direct labor hours
Step-by-step explanation: In simple words, direct labor hours refers to the standard amount of time that the labor takes to complete a task. It is a very common and has been used traditionally as an allocation base for the overhead costs.
Using this as a base, the accountant can allocate the overheads by allocating the per unit cost on the basis of direct labor hours worked in a particular span of time.
Hence, from the above we can conclude that the correct option is B.