听材料，回答问题。
（1）When did the Red Cross flag become a symbol of humanitarian aid in war？
A.In the early 19th century
B.During the First World War.
C.In the late 19th century.
（2）In which year was the American Red Cross found？
A.In 1881.
B.In 1904.
C.In 1999.
（3）Why did Clara Barton earn the nickname "Angel of the Battlefield"？
A.She was a real angel of heaven.
B.She tended the wounded in the line of fire.
C.She saved a lot of soldiers in the war.
（4）What happened to Clara Barton after war？
A.She became a president of the United States.
B.She set up American Red Cross and made it stronger.
C.She travelled to Europe for entertainment.