【单选题】

Why are the two brothers and the sister of Wilbur and Orville mentioned in paragraph 5
A．Because they all had more education.

B．To illustrate that the abilities and personal qualities of Wilbur and Orville had enable them to achieve their goals without college education.
C．To illustrate why it was not necessary for them to go to college.
D．To contrast the achievements of different family members.