The . . . . . . . . . ray passes through the axis of the fiber core.

The correct answer is: C. Meridional

A meridional ray is a ray that passes through the axis of the fiber core. It is the only type of ray that can propagate in a single-mode fiber.

A reflected ray is a ray that bounces off the surface of the fiber core. It is not able to propagate in a single-mode fiber.

A refracted ray is a ray that bends as it passes from one medium to another. It can propagate in a single-mode fiber if it is within the acceptance cone.

A Shew ray is a ray that is not able to propagate in a single-mode fiber. It is a type of reflected ray that is bent so much that it does not remain within the acceptance cone.