题目

下列关于酶的叙述，正确的是 A . 反应前后酶的数量不变 B . 酶的基本组成单位是氨基酸 C . 低温会破坏酶的分子结构 D . 酶不能脱离生物体起作用 答案：ARiding a London subway, a person from other countries will notice one major difference: in London, people do not look at each other．In fact, eye contact is avoided at all times. That’s not rudeness ― people are just too busy to bother looking． 　　Busy doing what, you ask? Well, they’re certainly not using the time for a moment of quiet thinking．Nor are they reading a book．New technology has replaced quiet habits．Today the only acceptable form of book on the London underground is an e-book． 　　Apple must earn a fortune from London commuters（使用月票上下班者）. Since the launch of the iPhone in 2007, over 40, 000 ― yes, 40, 000 “apps” have been designed． 　　Commuters love them because they are the perfect time - fillers. One “app”, called iShoot, is a game that features tanks．Another one, Tube Exits, tells passengers where to sit on the train to be closest to the exit of their destination. iSteam clouds the iPhone screen when you breathe into the microphone. You can then write in the “steam” on your phone screen． 　　For those without an iPhone, another Apple product, the iPod, may be the distraction (消遣) of choice. It’s not just teenagers who “plug in” to their music － iPods are a popular way to pass the time for all ages． 　　And if games, e-books and music aren’t enough to keep you occupied, then perhaps you would prefer a film? The development of palm DVD technology means many commuters watch their favorite TV shows or films on the way to work．With all these distractions, it’s amazing that people still remember to get off the train． 1.Those who want to save time to reach where they go can download ________ to their iPhones A. iShoot                         B. Tube Exits         C. iSteam               D. iPod 2.People in London do not make eye contact on the subway because ________． A. they are going to work and have no time to communicate with each other B. they love reading books and do not want to be disturbed C. they feel sleepy because of getting up early D. they’re busy playing games, reading e-books, listening to music or watching films 3.The underlined word “apps” in the third paragraph means ________． A. computers B. programs downloaded for the iPhone C. computer companies D. fortune from London commuters 4.The main idea of the passage is that ________． A. London commuters are unfriendly to strangers B. Apple has earned a lot of money from selling 40, 000 apps C. technology is changing how London commuters spend their traveling time D. riding a London subway is a must when visiting London