In [Cr(NH3)6]3+, Cr exists as Cr3+ ion. The outer orbital electronic configuration of Cr is 3d34S0. The orbital diagram is represented by
Here, X indicates lone pair of NH3 donated to Cr. Hence,
(a) d2−sp3 hybridization, octahedral. Thus, correct.
(b) There are three unpaired electrons, hence paramagnetic. Thus, correct.
(c) d2−sp3 inner orbital complex, thus incorrect.
(d) Due to ionizable Cl− ions, white precipitate with AgNO3, thus correct.