Out of benzene, m–dinitrobenzene and toluene which will undergo nitration most easily and why?

Which of the following undergoes nitration most easily?

Nitration is an example of aromatic electrophilic substitution and its rate depends upon the group already present in the benzene ring. Out of benzene and phenol, which one is more easily nitrated and why ?

Indicate the compound which can be nitrated most easily :

The compound which undergoes dehydration very easily is :

Which one of the following alcohols undergoes dehydration most easily?