Why is the ending of the story ironic, or the opposite of what you would expect? In the short story ‘Charles’

How did miss sullivan get helen to understand the connection between the world water and the actual object a. by holding helen's head under the water and forcing her to drink b. by spelling the world into helen's hands while pouring water over them c. by making helen drink many cups of water over a short period of time d. by talking to helen about the importance of drinking water everyday (apex)