题目

在地面上，将一个小球以v=20m/s初速度竖直上抛，则小球到达距抛出点10m的位置所经历的时间为（g=10m/s2）（） A . （2+ ）S B . （2﹣ ）S C . S D . （2+ ）S 答案：A,B,DGet a FREE YEAR ! Subscribe（订阅）and NOW get a FREE YEAR of Parents® magazine! That’s two full years （24 issues） for the regular one-year rate——just $12. But HURRY, this offer won’t last!（U. S. orders only, please. ）Every issue of PARENTS is filled with practical advice from leading doctors and child experts … toys and games that develop reader-tested products and more!100% Money-Back Guarantee: You must be pleased, or you may cancel any time during the life of your subscription and get all your money back——no questions asked. Parents® Magazine is published 12 times per year. Savings are based on $12.00 annual subscription rate. State taxes may apply to your order.E-mail address required to access your account and member benefits online. We will not share your e-mail address with anyone. Click here: www. parents, com/privacy to view our privacy policy.68. The purpose of the advertisement is ________.A. to help parents with their daily life    B. to attract more subscribersC. to collect money for children         D. to sell children toys and games69. Which of the following is true? A. Only $12 is paid for 24 issues of the magazine. B. Readers can get a free offer any time of the year. C. Readers from all over the world can enjoy the free offer. D. Readers can communicate with child experts on the Internet.70. A reader subscribed PARENTS three months ago, but now he finds the magazine dissatisfying. What can he do? A. He can cancel and get all his money back. B. He can cancel without getting money back. C. He can cancel after answering some questions. D. He can cancel at a certain time to get money back.71. Where can we most probably read the text? A. In a newspaper.                    B. In a website. C. In a science book.                  D. In a magazine.