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阅读理解 Washing habits have changed over theyears. In the 16th century, most people had a bath once a month…if they werelucky. Up until the 1950s, it was once a week. Only just recently has theconcept of daily showering become popular. But now, according to the New YorkTimes, things are changing again. The latest trend is known as soap-dodging.It basically consists of washing less, having fewer showers and using lesssoap. I just wash my hair once a month now, said Brett Dawson, a32-year-old management consultant. I have just one bath a week, saidMiriam Bayliss, a 28-year-old accountant.14．灯光下影子的形成是由于光在均匀介质中是沿直线传播的；光在真空中的传播速度是3×108m/s．