Some statement are given below

(I)  NH₃ is more polar than NF₃

(II) N$-$F bond is more polar than N$-$H bond 

(III) Formal charge on C atom in CO₂ is 4

(IV) Oxidation state of O atom in CO₂ is Zero

Among these statements

${\mathrm{\mu }}_{{\mathrm{NH}}_3}>{\mathrm{\mu }}_{{\mathrm{NF}}_3}$ hence NH₃ is more polar than NF₃

Electro negativity difference between N and F is more than N and H hence N-F bond is more polar than N-H bond

In CO₂ formal charge on C atom = $4-0-\frac{8}{2}$= 0

In CO₂ oxidation state of O atom = $-2$