The best explanation is:
A current will be induced because the wire moves through a magnetic field.
When a conductor (like a piece of wire) moves through a magnetic field, a change in magnetic flux occurs, which induces an electromotive force (EMF) and creates a current in the wire, according to Faraday's law of electromagnetic induction. The fact that the wire is unattached does not prevent the induction of a current; it simply means the wire is not part of a closed circuit, which may result in the current not being able to flow continuously. However, the act of moving through the magnetic field itself will still induce a voltage.