The answer is object permanence.
Object permanence refers to the ability to understand that an object is still present and physically exists even if it is hidden out of sight. In this example, your niece lacks object permanence since she does not understand that you are behind the blanket even though you cover yourself with it or you are temporarily.
Answer:
this is definitely difficult to understand at this point
Answer: Pain that increases with movement or pressure
Explanation: she is a tennis player, and tennis game involves movement. As a result of this injury to her joint, the consequence of this injury will not enable her to play tennis as "Pain will be developed as a result of movement and pressure
