You Have an 18-Month-Old Son and Your Friend Has a 12-Month-Old

You have an 18-month-old son and your friend has a 12-month-old son.You have been getting together each week for a couple of months for the children to socialize and so that you and your friend can talk.Your friend is concerned that his son is not very advanced because your son systematically and deliberately separates his various toys into categories while he plays and your friend's son is oblivious to any categories.What would you tell your friend?

A) His son should probably start going to a high-quality day care.
B) His son will most likely also categorize when he is 18 months old.
C) Your own son is very advanced as children generally do not categorize until they are at least 24 months old.
D) Infants are very different in their development.