The idea of micropayments--- charging Web users tiny amounts of money for single pieces of online content--- was basically put to sleep toward the end of the dot-com boom. In December 2000, Clay Shirky, a professor in New York University's interactive telecommunications program  , wrote a manifesto   that people still quote whenever someone suggests using the idea. "Micropayments will never work," he wrote, mainly because "users hate them."    But wait. Without many people noticing, micropayments have arrived--- just not in the way they were originally imagined. The 99 cents you pay for a song on the Internet is a micropayment. So are the tiny amounts that some operators of small web sites can earn whenever someone clicks on the ads on their pages. Some stock-photography companies sell pictures for as little as $1 each.    "Micropayments are here" said Benjamin M. Companie, a lecturer atprefix = st1 /NortheasternUniversity, "they just have not developed in the way that everybody expected."     From the earliest days of the Web until around the time of Mr Shirky's manifesto, the expectation was that a handful of companies would provide platforms---or perhaps a single platform--- that would enable Web users to pay a penny or a dollar for a bit of content such as a newspaper article, or a research report. Simply clicking a link would complete the transaction  .    Sellers of content--- at the time, newspaper companies---were among the most interested in the idea as they looked for tax income that didn't depend on advertising. You will have to pay for it, if you   _  . A) visit some famous websites B) read latest news on the internet C) advertise for your products on some websites D) download your favorite songs
C

If you look at the night sky, you'll often see stars moving very quickly. In fact, they move much more quickly than they should according to their size and the laws of physics. Scientists do not completely understand why the speed of these stars is so high. But many believe the reason is that much of the universe is made of something called "dark matter". Groups of stars called galaxies, such as the Milky Way, might even be made up of 90 percent dark matter. How much something weighs depends on where it is. The same object weighs only half as much on Mars as it does on Earth and almost three times as much on Jupiter. So scientists prefer to talk about the mass   of something rather than how much it weighs, because mass does not change. They can work out the mass of galaxies by measuring the distance between them and the speed they move at. Recently, Jorge Penarrubia, a senior academic at Edinburgh University, UK, and his team discovered something interesting: The mass of the Milky Way is only half as much as the mass of another nearby galaxy, Andromeda. This seems strange, and dark matter may explain why. Finding out more about dark matter could help us understand how the universe began, but this is not easy. Lots of scientists with different types of expert knowledge are working on the problem. We can't see dark matter, it's very difficult to measure and we can't find out its mass. Unlike stars, dark matter doesn't produce or reflect light. But we can make a good guess that it is there because of the way things move and the way light bends. Experts now think dark matter may be very different from the matter that we find on Earth. There may also be five times as much dark matter in the universe as ordinary matter. Something that weighs 15kg on Earth weighs about   _   on Mars and   _   on Jupiter. A) 7.5 kg; 45 kg B) 30 kg; 45 kg C) 45 kg; 7.5 kg D) 5 kg; 30 kg
A

The summer of 1975 I'd just graduated from college in Southern California and received a 1968 Ford Capri for a graduation present. I had my first job, in Los Angeles. One Sunday night, thinking myself a very independent gown-up, I left my uncle's place in South Laguna after a visit, without admitting to him that I had less than an eighth of a tank of gas and no cash to buy more on the way to L.A. I pulled onto the Pacific Coast Highway and watched the needle move down as I headed north. When the engine started giving off strong smells, I pulled into a gas station. There was no self-serve then; there were no credit cards, no ATMs. I begged the guy at the station. I could write him a check for gas, I said, or I could sleep in my car and try to walk to a town with a bank the next morning. As he was informing me that I could sleep in my car but he'd have me arrested, a station wagon pulled up to the next pump. The driver--a thin, plain, middle-aged guy--overheard the tail end of my failed request. As the attendant went to serve him, he nodded at me. "Fill her tank first," he said. "Really?" I said. Hope bloomed. "Oh, thank you. Thank you. But please. I just need two bucks' worth. I just need to get home." "Fill it," he repeated to the attendant. Then he turned to me, "You'll do the same one day, for someone else." The author had hoped that the gas station attendant would allow him to pay   _  . A) in cash B) by check C) by credit D) nothing

B