First of all you need to recall when an alcohol (-OH) is dehydrated, it forms alkenes (=).
Dehydration is an elimination process. In which OH being removed from one carbon and H from the adjacent carbon (beta-carbon). So in order to have two product there must be at least two carbon atoms adjacent to the alpha carbon.
Now you have to look for the option that gives two products.
We can easily eliminate the option A and C as it contains only one adjacent carbon atom.
Look at option D it has three carbon available to donate H-atom. But when it will be dehydrated all the products would have same structure. (See the picture attached)
Lastly, if we dehydrated the compound in option B (2-butanol) we will get two different products.