What does the given experimental set-up depict?
Choose the correct option accordingly.

Earthworms are ........

When a $J$-shaped conducting rod is rotating in its own plane with constant angular velocity $\omega$,about one of its ends $P$,in a uniform magnetic field $\vec B$ (directed normally into the plane of the paper),then the magnitude of the emf induced across it will be:

Among the following,the least stable resonance structure is

In the extraction of aluminium:
Process $X$: applied for red bauxite to remove iron oxide (chief impurity).
Process $Y$: (Serpeck's process) applied for white bauxite to remove $Z$ (chief impurity). Then,process $X$ and impurity $Z$ are:

Among the following,the compound that is both paramagnetic and coloured is