Pick out the correct statement with respect to [Mn(CN)_6]^3- :
1. It is \(sp^3d^2\) hybridised and tetrahedral
2. It is \(d^2sp^3\) hybridised and octahedral
3. It is \(dsp^2\) hybridised and square planar
4. It is \(sp^3d^2\) hybridised and octahedral