I believe the answer is C because it has multiple answers in one, and the most effective early childhood curriculum can have more than one solution.
Cerebrospinal fluid (CSF), clear, colourless liquid that fills and surrounds the brain and the spinal cord and provides a mechanical barrier against shock. Formed primarily in the ventricles of the brain, the cerebrospinal fluid supports the brain and provides lubrication between surrounding bones and the brain and spinal cord. When an individual suffers a head injury, the fluid acts as a cushion, dulling the force by distributing its impact. The fluid helps to maintain pressure within the cranium at a constant level.
https://www.britannica.com/science/cerebrospinal-fluid
C. H<span>ow hard a person works to do an activity.
Intensity has to do with effort. If a person works hard than they are intense, if vise versa than they are not intense.</span>