The IUPAC name of \(K _3\left[ Co \left( C _2 O _4\right)_3\right]\) is:

Potassium trioxalatocobaltate(III)

Potassium tris(oxalato)cobalt(III)

Potassium tris(oxalato)cobaltate(III)

Potassium trioxalatocobalt(III)