Don’t get confused between minimum drag, and minimum CD, the two are not the same!

Polar diagrams use coefficients to show how increasing/decreasing one variable affects the other variable. As g10 correctly states if you're not producing any lift, CL zero, then CD will be will be at a minimum. As you start to produce lift, CL increasing, then CD increases. There will be some point, shown as the tangent to the polar diagram, where the maximum CL is achieved for the minimum increase in CD. Not the minimum CD. This then is the best lift to drag ratio which occurs at Vmd, the bottom of the total drag curve.

Figure 11-3-16 shows the wing at its most efficient, best L/D ratio at 4 degrees alpha.

Going back to Luc's original query from Q294....this type of question is quite common where the answer you were looking for, Vmd, is not there and the examiner is using an alternative description of Vmd to test your knowledge.

For example when we look at the tangent to the power required curve we find that this is also Vmd, best range speed prop, but also described as the point where CL/CD is a maximum or where CD/CL is at a minimum.