Before attempting the exercise, click here to watch a short video.

The "assembly line" at Wheeled Coach is

A$.$ one line that allows workers to move up and down the line as necessary to keep the line balanced and moving.

B$.$ a series of $5$ lines that move in parallel.

C$.$ a series of lines that complete an ambulance every $5$ days.

D$.$ one line that completes $5$ ambulances every $8$ days.