= Solution
{c}
Undoped <gallium arsenide> is expected to be \b[diamagnetic] at zero <temperature>. Its <valence band> is filled and its <conduction band> empty, so there are no mobile <conduction band> <electrons> to give <Pauli paramagnetism>. The specified absence of localized <magnetic moments> removes a <Curie law> response and the usual mechanism for <ferromagnetic ordering>. The remaining induced orbital response is <diamagnetism>. This classification uses the ordinary weak-field <band insulator> picture; the <band gap> suppresses thermally generated carriers as $T\to0$.
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