题干

下列关于声的说法中,正确的是(  )

A:声音在空气中的传播速度为3×108m/s

B:只要物体在振动,我们就能听到其发出的声音

C:城区部分道路禁鸣喇叭,这是在声音传播的过程中减弱噪声

D:用超声波粉碎人体内的结石,说明声波具有能量

上一题 下一题 0.0难度 选择题 更新时间:2019-12-15 08:43:29

答案(点此获取答案解析)

D

同类题3

 Would you eat a ready meal from the fridge rather than cook by yourself ? Have you been doing Internet shopping rather than going to the stores?

 A study into how lazy British people are has found more than half of the adults are so lazy that they'd catch the lift rather than climb two flights of stairs.

 Just over 2,000 people were quizzed by independent researchers in the Britain's largest health center. The results were very surprising.

 About one in six people who were asked said if their control was broken, they would continue watching the same channel rather than get up.

  More than one third of those asked said they would not run to catch a bus. Worryingly, of 654 respondents (离婚被告) with children, 64% said they were often too tired to play with them.

  We know that it's no wonder that one in six children in the UK are very fat before they start school.

  Dr Sarah, Dauncey, medical director of the center, said, “People need to get fitter, not just for their own health, but for their families, friends and pets, too.”

 “If we don't start to take control of this problem, a whole generation will become too unfit to perform even the most basic tasks.”

  And Scotland's largest city, Glasgow, was shamed as the laziest city in the UK, with 75% asked thinking they do not get enough exercise, followed by Birmingham and Southampton, both with 67%.

  So there are some problems for the National Health Service, where fatness-related (相关的) illnesses such as heart disease and cancer have been on an increase for the past 40 years and are costing billions of pounds every year.