题目

如图，电源电压U = 220V，且保持不变， L1、L2、L3、L4都标有“PZ110V，40W”字样，开关断开时，四盏灯都能正常发光，若将开关闭合，下列叙述中正确的是A. L1、L3能正常发光 B. L1、L2、L3、L4都能正常发光C. L2、L4能正常发光 D. L1、L2、L3、L4都不能正常发光 答案：【答案】B【解析】开关闭合之后L1和L3并联，L2和L4并联，之后再串联。两部分电压为110V，故四盏灯都能正常发光，选B阅读理解（共20题； 每小题2分， 满分40分） 阅读下列短文，从每题所给的A、B、C 和D项中，选出最佳选项，并在答题卡上将该项涂黑。 They like using the Internet．They have lots of pocket money to spend．And they spend a higher proportion of it online than the rest of us．Teenagers are just the sort of people an online seller is interested in, and the things they want to buy－games, CDs and clothing－are easily sold on the Web. But paying online is a tricky business for consumers who are too young to own credit cards．Most have to use a parent’s card．They want a facility that allows them to spend money. That may come sooner than they think: new ways to take pocket money into cyber (网络的) space are coming out rapidly on both sides of the Atlantic．If successful, these products can stimulate online sales. In general, teenagers spend huge amounts: $153bn (billion) in the US last year and ￡20bn annually in the UK．Most teenagers have access to the Internet at home or at school－88 percent in the US, 69 percent in the UK．According to the Jupiter Research, one in eight of those with Internet access has bought something online－mainly CDs and books. In most cases, parents pay for these purchases with credit cards, an arrangement that is often unsatisfactory for them and their children．Pressing parents to spend online is less productive than pressing on the high street．They are more likely to ask “Why?” if you ask to spend some money online. One way to help teenagers change notes and coins into cybercash is through prepaid cards such as InternetCash in the US and Smart cards in the UK．Similar to those for pay-as-you-go mobile telephones, they are sold in amounts such as ￡20 or $50 with a concealed 14-digit number that can be used to load the cash into an online account. 1.What does the word “They” in paragraph 1 refer to?     A. Sellers.     B. Buyers.      C. Teenagers.      D. Parents. 2. According to the passage, which of the following statements is TRUE?     A. More than half of the teenagers in the US and the UK have Internet access.     B. Teenagers pay for goods online with their own credit cards.     C. Most teenagers in the US and the UK have bought something online.     D. Teenagers found it easier to persuade parents to buy online than in a shop. 3. A new way to help teenagers shop online is to use _________.     A. a new machine                  B. special coins and notes     C. prepaid cards                      D. pay-as-you-go mobile phones 4.What is the passage mainly about?     A. Online shopping traps.             B. Internet users in the US and the UK.     C. New credit cards for parents.       D. The arrival of cyber pocket money. 5. Which of the following words can best describe the writer’s attitude towards the phenomenon?     A. Proud and satisfied.            B. Worried and anxious.     C. Objective and informative.          D. Concerned and sad.