[单项选择]— Did you have difficulty finding John's house —Not really. John had given us good directions and we ______find it. A. would B. could C. had to D. were able to
参考答案:D 答案解析:[解题指要] 该题测试短语be able to与情态动词can的区别。表示过去有能力并实际上成功地做到某事,要用was/were able to,不用could。没有做到可用couldn’t或wasn
第11题: [单项选择]引起I型超敏反应的Ig是 A. IgM B. IgG C. IgD D. IgE E. SIgA 参考答案:D 答案解析:五类免疫球蛋白中,血清中含量最多的是IgC是抗感染的主要抗体,是惟一能通过胎盘的Ig;IgM在Ig中分子量最大,是个体发育过程中最早出现的Ig,天然血型抗体是IgM类;IgD是B细胞重要的膜受体之一;