An Explanation of the Importance of Individual Differences (Or of Unique

An explanation of the importance of individual differences (or of unique, non-shared events) in development would include all of the following concepts EXCEPT

A) genetically programmed biological maturation processes
B) the sensitive period, when an individual is influenced by the absence of a particular kind of experience
C) deviations from an individual's developmental pathway in the form of behavioural problems or mental illness
D) whether events in an individual's life have occurred "on-time" or "off-time"