Which Situation Most Closely Represents an Example of "Regression to the Mean

Which situation most closely represents an example of "regression to the mean"?

A) Two hearing-impaired parents produce a child who has normal hearing.
B) A 40-year-old man whose father developed type 2 diabetes mellitus at age 50 is diagnosed with the disorder.
C) The three children of a mother who has an intelligence quotient (IQ) of 170 all have IQs in the 110 to 120 range.
D) A child whose biologic parents are thin is adopted by a family whose members are obese and eventually becomes overweight.