A length-scale $(\ell)$ depends on the permittivity $(\varepsilon)$ of a dielectric material. Boltzman constant $\left(\mathrm{k}_{\mathrm{B}}\right)$, the absolute temperature (T), the number per unit volume (n) of certain charged particles and the charge (q) carried by each of the particles. Which of the following expression(s) for $\ell$ is(are) dimensionally correct?