Which one of the following compounds will be most readily dehydrated?

Acidic dehydration of alcohols involves the protonation of the alcohol followed by the loss of a water molecule to form a carbocation intermediate. This is the rate-determining step. The ease of dehydration is directly related to the stability of the carbocation formed. The order of stability of carbocations is Tertiary ($3^\circ$) > Secondary ($2^\circ$) > Primary ($1^\circ$) due to inductive and hyperconjugation effects. Consequently, the order of reactivity of alcohols towards dehydration is Tertiary > Secondary > Primary. Therefore, the compound that is a tertiary alcohol (or forms the most stable carbocation, such as allylic or benzylic) will be most readily dehydrated. (See NCERT Class 12, Unit 11, Section on Chemical Reactions of Alcohols; NCERT Class 11, Unit 12, Section 12.7.5 on Carbocation Stability).