A Schoolteacher Seeks Help from the School Psychologist Because a Child

A schoolteacher seeks help from the school psychologist because a child in her class is particularly unruly.The psychologist visits the class one day to observe the child.Knowing that she is being watched,the child is on her best behaviour.Which quality illustrated in this scenario makes it difficult for psychologists to study human behaviour?

A) The measure is reliable but lacks validity.
B) The measure is valid but lacks reliability.
C) The measure is reliable and valid.
D) The measure is neither reliable nor valid.