摘要
阅读下面的短文，然后从每题所给A、B、C、D四个选项中选择一个最佳选项。 Hemophilia(血友病) occurs when a gene(基因) fails to produce the protein needed for the blood to clot(凝块), or change from a liquid to a solid, The fault gene is passed from parents to children. People with hemophilia suffer uncontrolled bleeding. This can result in pain,
