cancer, according to the study published in the journal Cell Reports.

"If we can understand how these genomic changes (基因组变化) are contributing to cancer resistance, then we'll be able to start thinking about how we translate these to our patients." Joshua Schiffman, professor of pediatrics at University of Utah and an investigator at Huntsman Cancer Institute, said in an interview with CNN.

28. Why do elephants have a lower risk of dying from cancer than humans?

A. They have less "zombie genes".

B. They are huge enough to kill cells in damaged DNA.

C. They have more copies of a "master tumor suppressor" gene.

D. They eat less meat and more grass.

29. The "master tumor suppressor" gene brings the following benefits except that .

A. it can be transplanted into humans B. it can prolong elephants' lives

C. it can kill cells in damaged DNA D. it can bring "zombie genes" back to life

30. What does the underlined word "these" in the last paragraph refer to?

A. cells in damaged DNA B. cancer resistance

C. animals bodies D. genomic changes

31. What is still a "puzzle" for researchers?

A. Why we adopt the strategies to treat people.

B. How the genes defeat the cells in damaged DNA.

C. What kind of gene can kill the cancer

D. How many people die of cancer.

　　Lying alongside mountains of smelly garbage under the South American sun, Cateura is a long way from the music schools of Prague or Vienna. Yet the township, which grew out of Paraguay's largest dump (垃圾场), is gaining a reputation as a hothouse for musical talent - and for its youth orchestra that plays instruments made from garbage. "The world sends us garbage. We send back music," says Favio Chavez, leader of the "Recycled Orchestra". Orchestra members, poor children from Cateura, play violins fashioned from oven trays and guitars made from dessert dishes. The orchestra provides the youngsters an outlet and an escape, a chance to go beyond the mess of their slum through the music of Mozart, and even Sinatra. "In the beginning, it was difficult to play," says the 10-year-old violinist Celeste Fleitas. "But Favio helped me learn over time. From Favio, I have learned to be more responsible and value the things I have."

The destination for more than 1,500 tons of waste each day, the community has no safe drinking water and little access to electricity or sanitation (卫生设施). Illiteracy (文盲) is severe, and the children of the township often fall into drugs, violence and crimes.

　　Favio Chavez, a musical talent, came to Cateura as an environmental technician in 2006 and started a youth music school. He knew shop-bought instruments were beyond the means of villagers whose sheds are worth less than a violin, so he approached a carpenter to make some out of waste from the dump.

The orchestra caught the eye of Paraguayan filmmaker Alejandra Amarilla. She uploaded a