The correct answer 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 not used as the center of the circle). This forms our triangle.