Read the following article and select the best answer. Article: Ruby, the artist, is an Asian elephant, She is17 years old. She lives in the zoo. Ruby has produced about 100 paintings since last year. She has made more than $ 40,000 for the zoo. Zoo leaders say Ruby first showed the talent about four years ago. Zoo workers watched her make the marks in the sand with her trunk. She rubbed out the marks, then made the new ones. The zoo worker gave her brushes and paints. Soon Ruby painted pictures. Newspaper reporters wrote Ruby, then people asked about buying her pictures. And in this way, she made a lot of money for the zoo. This is how Ruby does the paintings. A zoo worker holds different color paints. Ruby touches the colors she wants. Then the worker gives her brushes with the chosen colors in her trunk and Ruby begins painting. Question: Ruby rubbed out the marks she had drawn in order to _ . - make other ones - clear her trunk - dig a hole in the sand - ask for brushes and paints
make other ones