题目内容：

Conventional wisdom says that hardship can make us before our time. In fact, a new study suggests that violence not only leaves long-term scars on children's bodies, but also changes their DNA, causing changes that equal to seven to ten years of premature aging (提前衰老).

“Scientists measured this by studying the ends of children' s chromosomes(染色体), called telomeres.” says Idan Shalev, lead author of a study published in Molecular Psychiatry.

Telomeres are special DNA sequences (序列)which prevent the DNA in chromosomes from separating. They get shorter each time a cell divides, until a cell cannot divide any more and dies.

Several factors have been found to shorten telomeres including smoking, radiation (辐射) and psychological stress(心理压力), such as being treated badly when young, and taking care of someone who is permanently ill.

In the study, researchers examined whether exposure to(暴露于) violence could make children' s telomeres shorten faster than normal. They interviewed the mothers of 236 children at the ages of 5, 7 and 10, asking whether the children had been exposed to violence between the mother and her partner, having been treated badly in a physical way by an adult, or bullying. Researchers measured the children's telomeres— in cells from their cheeks—at the ages of 5 and 10.

Telomeres shortened more quickly in children exposed to two or more types of violence, says Shalev. Unless such a pattern changes, the study suggests these children could be expected to develop diseases related to aging, such as heart attacks or memory loss, seven to ten years earlier than children of the same age.

Shalev says there is hope for these children. His study found that in some cases, telomeres can lengthen."Better exercise and stress reduction are three things that may be able to lengthen telomeres,” he says

1.The new study found that ________.

A. hardship has a long-term effect on a child's mind    B. violence leaves scars on a child's mind

C. violence can speed up a child's aging    D. hardship can change a child's DNA

2.According to the passage, telomeres ________.

A. are at the ends of people's chromosomes    B. can help prevent DNA from separating

C. can make a cell die quickly    D. become shorter before they die

3.What can we learn from the passage?

A. Violence can cause quick cell division in children’s body.

B. Children at the ages of 5 to 10 are more likely to be exposed to violence.

C. Being treated badly will make a child's telomeres shorten faster.

D. Children who have shorter telomeres may have a heart attack earlier.

4.What is the best title for the passage?

A. Violence Aging Children’s DNA.

B. Children’s Changing DNA Patterns

C. Violence and Telomeres

D. The Function of Telomeres