The relative rate of acid catalyzed dehydration of following alcohols would be

Rate of dehydration $\propto$ stability of first formed carbocation.

Carbocation formed from (III)…. stabilizes through resonance and hyper conjugation.

Carbocation formed from (I)….stabilizes through hyper conjugation and inductive effect.

Carbocations of (II) and (IV) are primary but stability of  (IV) is more eventhough it has less number of H.C hydrogens because it has strong +I group.