Which of the following overlap is the strongest?

σ bond is stronger than π bond.

In the given options 1, 2, 3 are σ-bonds.

As the size of p-orbitals increases, extent of overlapping decreases, and hence strength of the bond decreases.

From the above conclusions,

Extent of overlapping (or) [ Strength of overlapping]: 2p-2p > 3p-3p > 5p-5p > π[5p-5p]