Which one of the following is an inner orbital complex as well as diamagnetic in behaviour?
(Atomic no.:Zn=30, Cr=24, Co=27)
a. [Zn(NH₃)₆]²⁺
b. [Cr(NH₃)₆]³⁺
c. [Co(NH₃)₆]³⁺
d. None of the above