In the regression model below, we regress an individual's years of education on his/her father's years of education and his/her mother's years of education:

education=β₁+β₂educ_father+β₃educ_mother+u

What would the restriction  β₂+β₃=1 imply?

A. If one parent stayed in school for one more year while the education level of the other parent was held constant, we expect their child to complete one more year as well.

B. If the mother completed an additional year of education while the father did not, that would have the same predicted effect on the child as if the father completed an additional year of education while the mother did not. 

C. On average, a child's education equals the sum of both parents' education.

D. If both parents stayed in school for one more year, we expect their child to complete one more year of schooling as well.