Final answer:
In behavior analysis, the child's response 'ball' to the picture is a 'tact,' which is a verbal response to a visual stimulus; it is neither an echoic nor a mand.
Step-by-step explanation:
In the scenario where a student shows a picture of a ball and asks "what is this?" and the child responds with "Ball," the term 'ball' is referred to as a tact. A tact is a term used in behavior analysis to describe a verbal response that is under the control of a preceding visual or other sensory stimulus. In this case, seeing the picture of a ball evoked the response of saying the word 'ball.' It is not an echoic, as that would imply the child is mimicking the exact words of another person, nor is it a mand, which would indicate the word is being used as a command or request.