Ethan is making a short essay using the four types of sentences according to their purpose. He knows that a sentence is a group of words that is complete in itself. But , he has a problem. In his short essay, he is not sure it he will use the words "Go! ", "Yes!", and "Hello! " as sentences. How can we help Ethan? Can we consider "Go! ", "Yes! ", and "Hello! as sentences? Explain.​​