Question

the year 1917 was important for the wright brothers because their first successful flight occurred. their patent expired. they began to work for the army. they began to work for the british air force.

Explanation:

The Wright Brothers' first successful flight was in 1903. They began working for the U.S. Army (not the British Air Force) earlier than 1917. Their patent expired in 1917.

Answer:

their patent expired.