In a process cost system, transferred-in costs represent

A) manufacturing overhead costs applied to the products processed.
B) costs from external suppliers for materials used in processing.
C) direct labour and manufacturing overhead costs incurred in processing.
D) costs attached to partially completed units that have been received from a prior processing department.

Transferred-in costs in a process cost system are costs that are attached to partially completed units that have been received from a prior processing department. This means that these costs were incurred in a previous department and are being transferred to the current department to be further processed before being transferred again to the next department. They are not related to direct labor, manufacturing overhead, or materials from external suppliers.