If a piece of metal is thought to be a magnet,which one of the following observations would offer conclusive evidence?

$A$ thin rod of length $L$ is magnetized and has a magnetic moment $M$. The rod is then bent into a semicircular arc. The magnetic moment in the new shape is

If a bar magnet is cut along the dotted line as shown in the figure and the two pieces are held separated by a small distance as they are,then

Two short magnets of equal dipole moments $M$ are fastened perpendicularly at their centres. The magnitude of the magnetic field at a distance $d$ from the centre on the bisector of the right angle is ($\mu_0 =$ Permeability of free space).

$A$ bar magnet of length $l$ and magnetic dipole moment $M$ is bent in the form of an arc as shown in the figure. The new magnetic dipole moment will be

$A$ cylindrical magnetic rod has length $5 \ cm$ and diameter $1 \ cm$. It has uniform magnetization $M = 5.3 \times 10^{3} \ A/m$. Its net magnetic dipole moment is nearly (take $\pi = 22/7$):