How many city/cities of purely hilly region in Uttarakhand has/ have been designated as Municipal Corporation ?

The correct answer is (a) One.

The only city of purely hilly region in Uttarakhand that has been designated as Municipal Corporation is Dehradun. It was designated as a Municipal Corporation in 2000.

The other options are incorrect because they are not the correct number of cities of purely hilly region in Uttarakhand that have been designated as Municipal Corporation.