[QA] Why does the writer use the example of the aeroplane?

Question:

Why does the writer use the example of the aeroplane?

• A.
  Because he thinks it’s the most important invention inhistory.
• B.
  To show how an invention developed quickly.
• C.
  To explain how space travel started.
• D.
  To explain why transport changed in the 20^th century.