Here is the classification of the statements based on whether they are true in Euclidean or Spherical geometry:

1. Parallel lines do not intersect each other.

   • True in Euclidean Geometry.
   • False in Spherical Geometry.

   In Euclidean geometry, parallel lines never meet. However, in spherical geometry, lines (great circles) always intersect, meaning no parallel lines exist in the spherical sense.

2. Two straight lines may intersect at no more than one point.

   • True in Euclidean Geometry.
   • False in Spherical Geometry.

   In Euclidean geometry, two distinct straight lines can intersect at most once. In spherical geometry, two great circles intersect at exactly two points, so this statement does not hold.

3. The sum of the measures of the interior angles of a triangle can vary.

   • False in Euclidean Geometry.
   • True in Spherical Geometry.

   In Euclidean geometry, the sum of the angles in a triangle is always 180 degrees. In spherical geometry, the sum can vary and is always greater than 180 degrees depending on the size of the triangle.

Would you like further details or have any questions about these geometrical concepts?

Here are five related questions for exploration:

1. How are parallel lines defined in spherical geometry?
2. What happens to the angles in a quadrilateral in spherical geometry?
3. Can a triangle in spherical geometry have angles summing to 360 degrees?
4. Why is there no concept of parallel lines in spherical geometry?
5. How does curvature influence the behavior of straight lines in non-Euclidean geometries?

Tip: In spherical geometry, "lines" are represented by great circles, which always intersect at two points, fundamentally changing many properties compared to Euclidean geometry.