第10题: [单项选择]Questions 19 to 22 are based on the conversation you have just heard.A. She thinks she has good writing skills. B. She hopes she will have chances to improve. C. She is not confident with her writing skills. D. She thinks her writing skills are the best. 参考答案:A 答案解析:[解析] Q: How does the woman feel about her writing skills
第24题: [单项选择]用碱溶酸沉法提取香豆素类化合物的依据是香豆素( )。 A. 具有挥发性 B. 具有内酯环 C. 具有强亲水性 D. 具有强亲脂性 E. 含有酚羟基 参考答案:B 答案解析:[试题解析] 本题考查要点是“香豆素的提取与分离——碱溶酸沉法”。香豆素类及其苷因分子中具有内酯环,在热稀碱溶液中内酯环可以开环生成顺邻羟基桂皮酸盐,加酸又可重新闭环成为原来的内酯。所以,利用香豆素类