You have been assigned the task of developing a program for an automated storage system that can track the number of parts coming and leaving to establish the actual total number in stock. The type of counter you would program for this application would be a $($an$)\_\_\_\_\_\_\_\_\_\_\_\_$ counter.

Question $19$ options:

A$)$

up

B$)$

down

C$)$

timer

D$)$

up$-$down