题目

科学家在癌细胞培养液中加入维生素C（实验组）以研究其对癌细胞生长的影响．培养过程中定时检测处于分裂期细胞的百分比，得到如图曲线．据此分析，下列有关说法正确的是（ ） A . 癌细胞的出现是抑癌基因突变成原癌基因并表达的结果 B . 实验组细胞在15 h时对培养液中含氮、磷的物质吸收速率最快 C . 10 h时对照组中所有细胞的染色体数均为体细胞的2倍 D . 维生素C对癌细胞分裂间期的抑制作用比对分裂期的抑制作用明显阅读理解 　　If you have no special plans for your holidays, why not spend your time helping others? 　　Don't listen to people who say that young people today often think only of themselves. It's not true at all. More and more young people in the USA volunteer to spend their school holidays working for others. And they don' t do it for money. Here are some of their stories. 　　Alice Hamilton, 17 　　I'm going to help the Forest Centre build new hiking paths in the mountains. It's going to be terrific -- I'll spend the whole summer living in a tent and breathing the clean mountain air. I' m going to sleep under the stars. It will be a nice sport, and I'11 be able to do something good at the same time! 　　Jason Moore, 18 　　This summer, I'm going to volunteer with Special House Program. They build good, low-cost houses and sell them to families that are not very rich. They'll teach me what to do, so I'll help people and also have a chance to learn how to build houses. 　　Trish Anderson, 16 　　I'm going to teach kids who have trouble reading. I'll work for a program called Reading For Life. Every day, I'm going to help kids choose and read books that they like. I want to be a teacher, and I love children and reading, so this is going to be a great experience for me. (1)Young people in the USA volunteer to spend ________ helping others. [　　] A. school holidaysB. weekdays C. every morningD. every afternoon (2)What does Alice volunteer to do in summer? [　　] A. To sleep under the stars. B. To breath the clean mountain air C. To spend the whole summer living in a tent. D. To help build new hiking paths in the mountains. (3)From the passage, we know that Jason Moore ________. [　　] A. likes readingB. is 18 years old C. isn't very richD. is good at sport (4)wants to be a teacher. [　　] A. Alice HamiltonB. Jason Moore C. Trish AndersonD. None of them (5)Which is the most possible title for this passage? A. Reading for LifeB. A Special House Program C. The Forest CentreD. Young American Volunteers