Explanation:

The question asks for the greatest advantage of coaxial cabling. Coaxial cable has been a foundational technology for various networks and transmissions due to its specific characteristics. Option A, 'High security', is not its greatest advantage. While coaxial cable offers better shielding and thus more security against electromagnetic interference and casual eavesdropping than unshielded twisted pair, it is less secure than fiber optic cables and can still be tapped with specialized equipment. Option B, 'Physical dimensions', are often a disadvantage. Coaxial cables are typically thicker, heavier, and less flexible than twisted-pair cables, making them more challenging to install in tight spaces. Option C, 'Long distances', is a significant advantage of coaxial cabling. It can transmit signals over much longer distances than twisted-pair cables without requiring signal amplification or regeneration, due to its superior shielding and lower attenuation characteristics. This was a key benefit in early Ethernet networks and cable television. Option D, 'Easily tapped', is actually a disadvantage, not an advantage. While not as easy to tap as unshielded twisted pair, it is more vulnerable to tapping than fiber optic cables, which are extremely difficult to tap without detection. Therefore, the ability to transmit signals over long distances with less signal degradation is the most prominent advantage of coaxial cabling among the given choices.