At 12-24 months, the child is deemed a toddler. At this age, the rate of growth will slow, and the head growth rate will slow dramatically to about 1 inch every 6 months. What is the rate of head growth at this age?
1) 1 inch every 6 months
2) 1 inch every 3 months
3) 1 inch every 12 months
4) 1 inch every 9 months