Bond length and bond strength?

[Bigbirdo]

I used to think that shorter bond length leads to greater bond strength. I have seen that you can break the sp CH bond (III in this question), but not sp3 CC bond (II in this question), so I first guessed that 3 should be longer than 2 because it is easier to break. Obviously, I was wrong. Can you use bond length and bond strength to figure this question out? If yes, can someone please explain why I was wrong?

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[virajpatel]

Bond length decreases as bond strength increases. A triple bond is stronger than a double bond which is stronger than a single bond. This results in the bond becoming shorter as it becomes stronger. And in the case of the Br the larger the atom attached to the bond the longer the bond length.