"El perro bebe agua."
Translation:The dog drinks water.
If you want to generalize, you would be correct, but the lesson is asking for a specific answer. In other sections they ask for you to answer a similar question in a different but specific way. These are lessons. They are showing you subtle differences, all used, but all slightly different. And they want you to do all of them, as they say, so that you expand your hearing and speech!