Which of the following statements is true accordin

单项选择题

Every newborn baby is dealt a hand of cards which help to determine how long he or she will be allowed to play the game of life. Good cards will help those who have them to have a long and healthy existence, while bad cards will bring to those who have them terrible diseases like high blood pressure and heart disease. Occasionally, cards are dealt out that doom their holders to an early death. In the past, people never knew exactly which cards they had been dealt. They could guess at the future only by looking at the kind of health problems experienced by their parents or grandparents. Genetic testing, which makes it possible to find dangerous genes, has changed all this. But, until recently, if you were tested positive for a bad gene you were not obliged to reveal this to anyone else except in a few extreme circumstances. This month, however, Britain became the first country in the world to allow life insurers to ask for test results. So far, approval has been given only for a test for a fatal brain disorder known as Huntington"s disease. But ten other tests (for seven diseases) are already in use and are awaiting similar approval. The independent body that gives approval, the Department of Health"s genetics and insurance committee, does not have to decide whether the use of genetic information in insurance is ethical. It must judge only whether the tests are reliable to insurers. In the case of Huntington"s disease the answer is clear-cut. People unlucky enough to have this gene will die early, and cost life insurers dearly. This is only the start. Clear-cut genetic answers, where a gene is simply and directly related to a person"s risk of death, are uncommon. More usually, a group of genes is associated with the risk of developing a common disease, dependent on the presence of other genetic or environmental factors. But, as tests improve, it will become possible to predict whether or not a particular individual is at risk. In the next few years researchers will discover more and more about the functions of individual genes and what health risks — or benefits — are associated with them.

Which of the following statements is true according to the text

A．Genes may contribute to some common diseases.
B．Environmental factors cause more diseases than genes.
C．It is common that most fatal diseases are caused by genes.
D．It is impossible to get clear-cut genetic answers.