A glass rod of length L moves with velocity v perpendicular to a unif…

The correct answer is Option (3) → zero

A motional emf appears across a rod when the magnetic force pushes its free charge carriers towards one end, so that a potential difference builds up between the ends.

    \( \displaystyle F = qvB \)

In a metal rod the free electrons collect at one end until the electric field between the ends balances the magnetic force, giving \( \varepsilon = BLv \).

Glass is an insulator: its electrons are bound to their atoms and cannot move along the rod. No charges collect at the ends, so no potential difference develops and the induced emf across the glass rod is zero.

Note: The question does not say which meaning of “induced emf” it intends. The answer given by NTA takes it as the potential difference that builds up across the rod, which is zero for an insulator. Under the strict definition, the emf is the work done per unit charge by the magnetic force along the rod, \( \varepsilon = \int (\vec{v}\times\vec{B})\cdot d\vec{l} = BLv \), which does not depend on the material of the rod; under that reading Option (2) would also be correct.