Bridge-head hydrogen refers to the hydrogen atom attached to the carbon atom that is part of a bridging group in a molecule. In the case of cis-decalin, which is a bicyclic compound consisting of two cyclohexane rings connected by a bridge, the bridgehead hydrogen is the hydrogen atom attached to the carbon atom at the bridgehead position.

The positioning of the bridgehead hydrogen in cis-decalin can be determined by analyzing the conformation of the molecule. The conformation refers to the spatial arrangement of the atoms in a molecule, specifically the arrangement of the substituents around each carbon atom.

In the case of cis-decalin, the two cyclohexane rings can adopt different conformations, specifically the chair conformation. The chair conformation is the most stable conformation for cyclohexane due to the minimization of steric interactions between the substituents. In the chair conformation, the cyclohexane rings adopt a chair-like shape with alternating axial and equatorial positions for the substituents.

To determine the positioning of the bridgehead hydrogen, we need to consider the conformation of cis-decalin. In the chair conformation, the bridgehead carbon atom is part of the bridging group, and it is connected to two other carbon atoms within the molecule.

Considering the spatial arrangement of the substituents in the chair conformation, we can determine the positioning of the bridgehead hydrogen as follows:

- The substituents attached to the bridgehead carbon atom are in an axial and equatorial position relative to the bridgehead hydrogen.
- The axial position refers to a substituent that is perpendicular to the plane of the cyclohexane ring, while the equatorial position refers to a substituent that is in the plane of the cyclohexane ring.
- Since the bridgehead carbon atom is connected to two other carbon atoms within the molecule, one of the substituents will necessarily be in an axial position, while the other will be in an equatorial position.
- Therefore, the bridgehead hydrogen is positioned as axial and equatorial.

In conclusion, the correct answer is option C: Axial, Equatorial.