What logically could have gone wrong?

The steps to construct a circle circumscribing a triangle are:

- Construct a perpendicular bisector of one side of the triangle
- Construct another perpendicular bisector of another side of the triangle
- The point of intersection of these two perpendicular bisectors is the center
  of the circle, we are about to construct.
- Adjust the width of the compass between the intersection point to any of
  the corners of the triangle. This width should be the same for all three
  vertices
- With the pointer of the compass is located at the intersection point, construct the circle

What could possibly go wrong when the  circle only passes two vertices, is the width of the compasses has changed while constructing the circle

First option

For the first question the answer is a, for the second c, for the third d, for the 4th b, for the 5th a