A student made a plan diagram of some plant tissue. The diagram is shown. There is an error in the way it has been drawn. The maximum width of R is 15 mm on the diagram and its actual width is 250 $\mu$m. The student was asked to add a scale bar to their diagram. Which row is correct?
- Aroot, phloem, 6
- Broot, xylem, 170
- Cstem, phloem, 170
- Dstem, xylem, 6