【单选题】

Which of the following is not the example of applying the threshold method
A．Parents introduce spinach in small bites or mixed with a food that the child enjoys over time so that the child will not refuse to eat it.

B．Teachers introduce academic content in short blocks of time for young children and gradually increase session length but not to where students become frustrated or bored.
C．Paper with wider lines is first used and then paper with narrow lines is introduced step by step to help children learn printing and handwriting.
D．A child might be made to throw toys until it is no longer fun by his parents in order to change his behavior of repeatedly throwing toys.