Which one of the following is an outer orbital complex and exhibits paramagnetic behaviour :

Question

( A ) $[Co(NH_3)_6]^{ 3+}$
( B ) $[Cr(NH_3)_6]^{ 3+}$
( C ) $[Zn(NH_3)_6] ^{2+}$
( D ) $[Ni(NH_3)_6]^ {2+}$