Question

arrange the set of bonds according to length. longest bond c≡c c=c c−c shortest bond

Explanation:

Step1: Recall bond - length principle

Bond length is inversely related to bond order.

Step2: Determine bond orders

The bond order of $C - C$ is 1, of $C = C$ is 2, and of $C\equiv C$ is 3.

Step3: Arrange by length

Since higher bond - order means shorter bond length, the order from longest to shortest is $C - C>C = C>C\equiv C$.

Answer:

Longest bond: $C - C$
Middle - length bond: $C = C$
Shortest bond: $C\equiv C$