13Dekho, 4 is the most stable, followed immediately by 2 ...as there is possibility of resonance of the free radical with the = bonds (allylic radicals).
5 - is least stable, as the aromaticity of benzene is being hindered.
Only, 1, 3 left.... So, here a secondary free radical is stabler than a secondary vinylic free radical => 1 stabler than 3.
Hence, the order.