What type of narrator should an author use if he or she want to focus on the thoughts and feelings of only one character

Any  writer who wants to point out the feelings and attitudes of one character in special should use a first person narrator. First person narrators know what is happening in a story .They have such a clear vision of what is going on that they reflect their feelings in their words. They  charge their words with emotions they experience at every moment of the action that takes place. First person narrators mention what they do and why they act in a certain way or the other.That maily provides the basis for having the feelings expressed as the events happen in a story.   It is simply impossible to disconnect the first person narrator from the way they feel.Using a first person narrator will give you the opportunity  of focusing directly on the thoughts and emotions of one character!