听一段材料,回答下面几个小题。
When did Grandma Moses turn to painting?
A. At the age of 76.
B. At the age of 39.
C. At the age of 101.
What did Grandma Moses do before she became an artist?
A. She sold her works for a little money.
B. She worked on her farm.
C. She taught at a school.
What is the story mainly about?
A. A famous American artist.
B. Making money from painting.
C. Collecting paintings.