A. While all the top polygons from step 15 are still selected, click the Grow button in the Selection section of the Modify tab three times.

B. Select the Select Invert option from the Edit menu.

C. Deselect the three rows of polygons as shown in the image below by holding the ALT key and drawing a selection rectangle.

D. Click the Grow button in the Selection section of the Modify tab two times and click the Shrink button next to it also two times. Now you should end up with the polygons being selected as shown in the following image.