The correct option is A IV>II>I>III
Rate of dehydration of the given compounds depends on the stability of the carbocation formed.
Compound IV form most stable allylic carbocation, hence, it undergo dehydration rapidly.
Compound III will form very unstable anti-aromatic carbocation as an inytermediate. Hence it has the least tendency to undergo dehydration.
Comparing compound I and II, carbocation of II is tertiary, hence, it is stable than carbocation of I.
Therefore, the correct order of dehydration is
IV>II>I>III