Answer:
a) token economy
Step-by-step explanation:
Token economy is a way of management which is run by the continuously reinforcing the behavior of a person. The thing which is used to continuously reinforcing the behavior is called a token. Token economy is based on operant conditioning and behavioral economics.
Here, the behavior of the children of memorizing the poem and reciting it is being encouraged by the use of stickers. The stickers here are the tokens.