题目

下图为某种自行车的链轮、链条、飞轮、踏板、后轮示意图，在骑行过程中，踏板和链轮同轴转动、飞轮和后轮同轴转动，已知链轮与飞轮的半径之比为3:1，后轮直径为660mm，当脚踩踏板做匀速圆周运动的角速度为5rad/s时，后轮边缘处A点的线速度和向心加速度为( )A. v＝9.90 m/sB. a＝148.50 m/s2C. v＝4.95 m/sD. a＝74.25 m/s2 More American people take their troubles with them on holiday, according to a new survey. Although 40 percent said that the main reason for going away is to escape pressure(压力) from work, almost all said they worry more than they do at home. Only four in every 100 said that they are happy and free of care. The most common worry is burglary(入室盗窃), with four out of 10 worrying about their homes being broken into while they' re abroad. More than a quarter fear they will feel crazy with some other noisy and rough holiday-makers and 22 percent worry they may be attacked or their possessions will be missing. One in five think the car may break down, and the same number worry about the chances of bad weather. The survey also showed that the stay-at-home Americans are no more. Three out of every five want to have a holiday abroad, a great increase from the figures only three years ago. The hotel holiday is still a winner, with about one third of all Americans preferring to go on a self-catering(自助) holiday. 1.The underlined word "survey" in the first paragraph most probably means _______ A. research          B. review             C. exhibition         D. examination 2.According to the text, about _____ of people worry more on holiday than when they are at home. A. 25%              B. 40%               C. 80%              D. 95% 3.The third most common worry of American holiday-makers is that they may______ A. be attacked or lose their possessions       B. have problems with their cam on the road C. have bad weather on holiday                  D. get mixed with some rough fellow holiday-makers 4.Where do American holiday-makers like to stay most? A. At a hotel.                              B. In a quiet place. , C. At a friend' s house.                        D, Where they can cook for themselves.