Drinking alcohol is a socially acceptable behavior in many parts of the world. Some medical experts say light drinking may even be good for your health, especially for the heart. But they say such health benefits should be compared to the many health risks connected with alcohol use. Some research suggests that having one to two drinks of alcohol a day may offer some health benefits. Several large studies have shown that this type of moderate  drinking may lower the risk of heart disease and other diseases. A study last year suggested that drinking small amounts of red wine may help lower the risk of breast cancer in women. Researchers at Medical Center in California studied 36 women. Each woman drank a glass of red or white wine every day for almost a month. Researchers collected blood samples from the women two times a month to measure their hormone  levels. The next month the women who drank red wine were told to drink white wine instead. The white wine drinkers were told to drink red wine. The researchers found that the women who drank red wine had lower levels of the female hormone than the white wine drinkers. They said red grapes have chemicals that may help to lower the risk of breast cancer. However, recent studies suggested that even small amounts of alcohol may generally increase the risk of breast cancer in women. They found that women who drink four small glasses of wine a week increase their risk of breast cancer by 15 percent. Many studies have examined the harmful effects of alcohol use on the body. Alicia Ann Kowalchuk serves as medical director, saying "Healthy use for adults --- that's men under age 65 --- is no more than 4 drinks in a day and no more than 14 drinks in a week. And for women of all ages, it's no more than 7 drinks in a week and no more than 2 drinks in a day." She says too much alcohol use has been linked to liver diseases, and many other cancers. How did the researchers carry out their study?
By following an example. By listing facts. By collecting information worldwide. By comparing tested objects.
Question: Drinking alcohol is a socially acceptable behavior in many parts of the world. Some medical experts say light drinking may even be good for your health, especially for the heart. But they say such health benefits should be compared to the many health risks connected with alcohol use. Some research suggests that having one to two drinks of alcohol a day may offer some health benefits. Several large studies have shown that this type of moderate  drinking may lower the risk of heart disease and other diseases. A study last year suggested that drinking small amounts of red wine may help lower the risk of breast cancer in women. Researchers at Medical Center in California studied 36 women. Each woman drank a glass of red or white wine every day for almost a month. Researchers collected blood samples from the women two times a month to measure their hormone  levels. The next month the women who drank red wine were told to drink white wine instead. The white wine drinkers were told to drink red wine. The researchers found that the women who drank red wine had lower levels of the female hormone than the white wine drinkers. They said red grapes have chemicals that may help to lower the risk of breast cancer. However, recent studies suggested that even small amounts of alcohol may generally increase the risk of breast cancer in women. They found that women who drink four small glasses of wine a week increase their risk of breast cancer by 15 percent. Many studies have examined the harmful effects of alcohol use on the body. Alicia Ann Kowalchuk serves as medical director, saying "Healthy use for adults --- that's men under age 65 --- is no more than 4 drinks in a day and no more than 14 drinks in a week. And for women of all ages, it's no more than 7 drinks in a week and no more than 2 drinks in a day." She says too much alcohol use has been linked to liver diseases, and many other cancers. How did the researchers carry out their study?
A. By following an example.
B. By listing facts.
C. By collecting information worldwide.
D. By comparing tested objects.
Answer: