Correct order of bond length is-
CO2−3>CO2>CO
Let's take a look at the structure of CO2−3, CO2 and CO
CO2⇒..O..=C=..O..
CO⇒:C≡O:
So, bond order will be:
CO2−3⇒1.33
CO2⇒2
CO⇒3
We know,
CO> CO2 >CO2−3(Bond Order)
We know
Bond order∝1Bond Length
⇒CO2−3>CO2>CO(Bond Length)