The <em><u>correct answer</u></em> is:
Without changing the span on the compass, place the compass point on one endpoint of the diameter and draw a full circle.
Explanation:
The steps to construct an inscribed equilateral triangle using the diameter are:
1. Place your compass point on the paper and draw a circle. Be sure to keep the compass set at the same width.
2. Using a straightedge, draw the diameter of the circle.
3. With the compass still set to the same width, place the compass point on one endpoint of the diameter and draw a full circle.
4. Draw segments connecting the points of intersection of the two circles and connecting each of these points to the opposite end of the diameter (the one <em>not</em> used as the center of the circle). This forms our triangle.