$1\mathrm{.}2\mathrm{.}19$ Consider two semiconductor samples $($with same $E_g)$ doped at the same density with different donor$-$type impurities with different ionization energies. There are no acceptor atoms in the semiconductors. In both samples donor ionization energy $E_c-E_D>0eV$ and $E_c-E_v>E_c-E_D.$

i$)$ both semiconductors are perfect insulators at $T=0K+$

ii$)$ the boundaries $($temperatures$)$ between the ionization and extrinsic regions are equal in the samples

iii$)$ the boundaries $($temperatures$)$ between the extrinsic anld intrinsic regions are nearly equal in the samples $+$

a$)$ i and iii

b$)$ ii and iii

c$)$ only i

d$)$ i and ii

e$)$ i$,$ ii and iii

$1-50$