Answer:
[Cr(NH3)6.]C13
Step-by-step explanation:
Alfred Werner's coordination theory (1893) recognized two kinds of valency;
Primary valency which are nondirectional and secondary valency which are directional.
Hence, the number of counter ions precipitated from a complex depends on the primary valency of the central metal ion in the complex.
We must note that it is only these counter ions that occur outside the coordination sphere that can be precipitated by AgNO3.
If we consider the options carefully, only [Cr(NH3)6.]C13 possess counter ions outside the coordination sphere which can be precipitated when treated with aqueous AgNO3.