The value of the 'spin only' magnetic moment for one of the following configurations is $2.84\text{BM}$. The correct one is:

1. A
   $d^4$ (in strong ligand field)
2. B
   $d^4$ (in weak ligand field)
3. C
   $d^3$ (in weak as well as in strong fields)
4. D
   $d^5$ (in strong ligand field)