The correct option is A [Co(NH2)2(NH3)4]OC2H5
The cation is always named before the anion!
Since we know that ethoxide C2H5O− is the anion (with a single negative charge),
the cation must be a complex with a single positive charge.
The given name can be broken into as:
Di-amido ⇒ as in there are two amide groups - NH−2.
tetraammine ⇒ which implies there are 4 NH3 groups!
The central metal of the complex cation is Co(III)
Hence: [Co(NH2)2(NH3)4]OC2H5