To select all of the boxes of an organization chart

Answer: Option B

To select all of the boxes in an organization chart in PowerPoint, you should use Option B: Right click the chart background and then click select all. This method allows you to select all elements within the organization chart quickly.
Option A: Clicking and edit and select all is not the standard method for selecting all boxes in an organization chart.
Option C: Press and hold the SHIFT key and click each box is inefficient for selecting all boxes, as it requires selecting each box individually.
Option D: All of above is incorrect because Options A and C are not practical methods for selecting all boxes in an organization chart.
Therefore, the correct answer in this context is Option B: Right click the chart background and then click select all.