题目

Many Chinese students who have learnt English for more than ten years are still unable to speak English very well when they meet a foreigner. They seem to have mastered the basic language structure(结构), but a conversation in English will make them feel uneasy. They are afraid that other people might find out their mistakes.   It's uncommon that many students who are bad speakers of English can write English perfectly. This proves that they are unable to organize their idea in English. The center of the problem is that they lack practice and confidence (自信).   Why should you be afraid一对表现型正常的夫妇，他们的双亲中都有由半乳糖血症引起的痴呆病患者。这是一种常染色体隐性遗传病。预期他们生育一个患半乳糖血症的女孩的儿率是A.12.5％B.25％C.50％D.75％