Want to reduce your risk of skin cancer? Wear sun screen, of course. But two new studies suggest that choosing your relatives carefully could also be helpful. One found that having an identical (同卵的) twin with melanoma (黑色素瘤) increased a person's own risk of developing the disease much more than having a fraternal (异卵的) twin with this type of skin cancer. The other found that having a brother or sister, or a parent with one of several different types of non-melanoma skin cancer increased risk as well. Several studies have suggested melanoma and other skin cancers run in families, but it can be difficult to tell the difference between the influence of genes and environment. In the Australian study, Dr. Sri N. Shekar of the University of Queensland and his colleagues attempted to do so by looking at twin pairs in which at least one brother or sister had been diagnosed with melanoma. They searched through thousands of cases of melanoma reported in Queensland and New South Wales and found 125 twin pairs. In four of the 27 identical twin pairs, both had melanoma, while three of the 98 fraternal twin pairs had both been diagnosed with the deadly skin cancer. Based on these numbers, having an identical twin with melanoma increased a person's own risk of the disease nearly 10-fold. This suggests, the researchers say, that some of the increased melanoma risk can be attributed to genes, in particular interactions between genes. They estimate that genes account for about half of the differences in risk between two people. In the second study, Dr. Shehnaz K. Hussain of the University of California and colleagues looked at the Swedish Family-Cancer Database to estimate the risk for several types of skin cancer among brothers or sisters and children of people diagnosed with these diseases. They found that people with a brother or sister, or a parent diagnosed with some types of skin cancer were more likely to develop skin cancers of various types, not just the ones their relatives had. When tumors occurred at parts of the body more likely to have been exposed to the sun, the family risk was stronger.1. Based on the statistics in Para. 4, it can be inferred that ________.A) skin cancer can be infectious among family membersB) most people who have twin brothers or sisters will have a certain type of skin cancerC) people having twin brothers are more likely to have skin cancer than those who have twin sistersD) people having identical twin brothers or sisters are more likely to have skin cancer than those who have none 2. According to the passage, deadly skin cancer is caused by ________.A) gene B) environmentC) exposure to the sunD) identical twins with melanoma3. In the second study, Dr. Hussain found ________.A) that different types of skin cancer are mainly due to the environmentB) that family members could develop more than one type of skin cancer C) that exposure to the sun is beneficial to skin cancer preventionD) that family members tend to develop the same type of skin cancer4. It can be inferred from the passage that ________.A) the research by Dr. Hussain goes against Dr. Shekar's findingsB) parents who have identical twins are most likely to be victims of skin cancerC) Australia has the richest database of twins family in the worldD) interaction between genes may partially account for developing skin cancer 5. What is the main idea of the passage?A) Melanoma is a type of deadly skin cancer.B) Researchers found that skin cancer can be inherited. C) Both environment and genes cause the risk of skin cancer.D) Australian scientists made a breakthrough in the treatment of skin cancer.