Covington Corporation uses a process$-$cost accounting system. The company adds direct materials at the start of its production process; conversion cost, on the other hand, is incurred evenly throughout manufacturing. The firm has no beginning work$-$in$-$process inventory; its ending work in process is $80\%$ complete. Which of the following sets of percentages would be used to calculate the correct number of equivalent units in the ending work$-$in$-$process inventory?

A$.$ Materials, $100\%$; conversion cost, $20\%.$

B$.$ Materials, $80\%$; conversion cost, $80\%.$

C$.$ Materials, $100\%$; conversion cost, $100\%.$

D$.$ Materials, $100\%$; conversion cost, $80\%.$

E$.$ Materials, $80\%$; conversion cost, $100\%.$