Which material susceptibility would be classified as diamagnetic?

Diamagnetic materials are characterized by a negative magnetic susceptibility, which indicates that they create a magnetic field in opposition to an external magnetic field. This results in a repulsion from the magnetic field. The value of magnetic susceptibility can be expressed in terms of numerical values, where negative values signify diamagnetism.

In the provided choices, the first option corresponds to a susceptibility value of -2.5×10^-5, which is indeed negative and classifies it as diamagnetic. This means that when placed in a magnetic field, this material would be slightly repelled, demonstrating the defining characteristic of diamagnetic substances.

The other options, displaying positive susceptibility values, indicate that those materials would exhibit paramagnetic or ferromagnetic properties, which involve attraction to the magnetic field rather than repulsion. Thus, the focus on the negative susceptibility value helps firmly establish that the correct classification of diamagnetic material belongs to the first option.