Increasing order of the following stability is:
(a)   I > II > III > IV                  (b) I > III > II >IV
(b)   I > IV > III > II                  (d) IV > III > II > I

Here all alkenes are equally substituted (disubstituted)  so we need to check hyperconjugation effect  with the pi electron density .This depends on the number of H atoms on the carbon(sp3) bonded to sp2 carbon of the double bond.
Structure I   --3 Hs for hyperconjugation
Structure II   --2 Hs for hyperconjugation
Structure III   --1 H for hyperconjugation
Structure IV   -- none H for hyperconjugation