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阅读理解。

     At age 61, identical twins Jeanne and Susan no longer look exactly alike. Susan smoked for many years

and is an admitted sun worshipper, whose habits Jeanne does not share. A new study of twins suggests you

can blame those coarse (粗糙的) wrinkles, brown or pink spots on too much time in the sun, smoking, and

being overweight.

     Because twins share genes, but may have different exposures to environmental factors, studying twins

allows an "opportunity to control for genetic susceptibility (易受影响性)," Dr. Elma D. Baron, at Case

Western Reserve School of Medicine in Cleveland, Ohio, and his colleagues explain in the Jatest issue of

Archives of Dermatology.

     Their analysis of environmental skin-damaging factors in 65 pairs of twins hints that skin aging is related

more to environment and lifestyle than genetic factors.

     But when it comes to skin cancer, the researchers say their findings support previous reports that both

environment and genes affect skin cancer risk.

     Baron's team examined facial skin of 130 twins, 18 to 77 years old, who lived mostly in the northern

Midwest and Eastern regions of the US, who were attending the Twins Days Festivalin Ohio in August 2002.

At this time, each of the twins also separately reported how their skin burned or tanned (晒黑) without

sunscreen, their weight, and their history of skin cancer, smoking, and alcohol drinking. The study group

consisted of 52 fraternal (异卵双生) and 10 identical twin pairs, plus 3 pairs who were unsure of their twin

status.

     From these data, the researchers noted strong ties, outside of twin status, between smoking, older age,

and being overweight, and having facial skin with evidence of environmental damage. By contrast, sunscreen

use and drinking alcohol appeared related to less skin damage.

     Baron and his colleagues say the current findings, which highlight ties between facial aging and potentially

avoidable environmental factors-such as smoking, being overweight, and unprotected overexposure to the

sun's damaging rays-may help motivate people to minimize these risky behaviors.

1. Which of the following is true according to the passage?[ ]

A. Jeanne and Susan share all the habits including smoking.

B. Skin aging is related more to environment and lifestyle than genetic factors.

C. Only identical twins can take part in the research.

D. Sunscreen use cannot help people have less skin damage.

2. Why did Baron's team do the research on twins? [ ]

A. Twins are more likely to suffer from skin cancer.

B. It may guarantee the research is not influenced by genetic factors.

C. It gives others an opportunity to control twins' genes.

D. It helps find twins are exposed to different environments.

3. What can you infer from the last paragraph? [ ]

A. This research makes people aware of dangerous lifestyles.

B. The environmental factors are unavoidable.

C. Being exposed to the sun is absolutely damaging.

D. There is little relationship between skin aging and environment.

4. The passage is mainly concerned with _____.[ ]

A. skin cancer and environment 

B. identical twins research

C. aging skin and environmental factors

D. genes and lifestyles

下列说法正确的是（　　）

A．支点一定在杠杆上

B．力臂一定在杠杆上

C．动力作用点与阻力作用点一定在支点的两侧

D．杠杆的长度一定是动力臂与阻力臂之和

简述房间隔缺损的分型及超声诊断

证券投资风险与收益的确定和证券投资决策是以（）为前提的

A．会计主体假设

B．投资风险假设

C．风险与收益均衡假说

D．效率市场假说

3～4岁的学前儿童能够双脚交替地下楼梯。