Give the decreasing order of the stabilities of the following :

Explanation

(a) `iii gt i gt ii(3^@ gt 2^@ gt 1^@)`
(b) `iv gt ii gt igt iii gt v (2^@` allylic and resonance `gt 2^@` allylic `gt 2^@` vinylic `gt dot C_6 H_5)`
( c) `iii gt ii gt iv gt igt (2^@` allylic `gt 1^@` vinylic)
(d) `beta gt gamma gt alpha` (vinylic `H gt 2^@ H gt` allylic `H)` (The larger is the bond energy, the less stable are the species).