Step 1: Revisiting the bond order equation.
Bond order = (Nb - Na) / 2, where Nb denotes bonding electrons and Na antibonding electrons.
Step 2: Defining the CO reference.
Let the bond order of CO be x, serving as the proportional baseline.
Step 3: Determining N₂⁺ bond order.
Neutral N₂ has a bond order of 3; removing one electron to form the cation slightly alters it, expressible as 5x/6 relative to CO.
Step 4: Determining C₂ bond order.
Molecular orbital assessment of C₂ gives a bond order of 2, which proportionally equates to 2x/3.
Step 5: Matching with the provided alternatives.
Option (4) correctly states N₂⁺ = 5x/6 and C₂ = 2x/3.
Step 6: Conclusion.
Thus, the respective bond orders are 5x/6 and 2x/3.