关于运动的性质，以下说法中正确的是（   ）

    Almost every machine with moving parts has wheels, yet no one knows exactly when the first wheel was invented or what it was used for. We do know, however, that they existed over 5,500 years ago in ancient Asia.

    The oldest known transport wheel was discovered in 2002 in Slovenia. It is over 5,100 years old. Evidence suggests that wheels for transport didn't become popular for a while, though. This could be because animals did a perfectly good job of carrying farming tools and humans around.

    But it could also be because of a difficult situation. While wheels need to roll on smooth surfaces, roads with smooth surfaces weren't going to be constructed until there was plenty of demand for them. Eventually, road surfaces did become smoother, but this difficult situation appeared again a few centuries later. There had been no important changes in wheel and vehicle design before the arrival of modem road design.

    In the mid-1700s, a Frenchman came up with a new design of road—a base layer (层) of large stones covered with a thin layer of smaller stones. A Scotsman improved on this design in the 1820s and a strong, lasting road surface became a reality. At around the same lime, metal hubs (the central part of a wheel) came into being, followed by the pneumatic tyre(充气轮胎) in 1846. Alloy wheels were invented in 1967, sixty years after the appearance of tarmacked roads (柏油路). As wheel design took off, vehicles got faster and faster.

    The wedding tradition of “something old, something new, something borrowed and something blue” has been around for hundreds of years. The tradition of carrying or wearing one of each item is said to bring luck and fortune to the newly married couple. Have you ever stopped to think what the saying really means? What is its origin and what does each item represent?

    The original saying dates back to the Victoria times and states, “something old, something new, something borrowed, something blue and a silver sixpence in your shoe.”

    Something old   A bride may wear or carry something old to represent her continued ties to her family and her old life. Many brides wear a piece of family jewelry as their old item. Some brides wear the wedding dress worn by their mother or grandmother. In many cases, something old may also be something borrowed.

    Something new   Wearing something new is supposed to represent success and hope in the bride's new life and in her marriage. If the bride purchased her wedding dress new, it may represent her new item, but any item that is new may be used. Something “new” is usually the easiest kind to fill.

    Something borrowed   The borrowed item should be something borrowed from a friend that is happily married. It is said that their happiness will rub off on you and bring lasting happiness to your marriage. Some brides borrow an item of clothing, a piece of jewelry, a handkerchief or perhaps a beaded(带珠子的) purse.

    Something blue Wearing something blue dates back to ancient times when a blue wedding dress was worn to represent purity, fidelity and love.

    Silver sixpence   Placing a silver sixpence in the bride's left shoe is said to be a symbol of wealth. This not only refers to financial wealth, but also a wealth of happiness and joy throughout her married life. Since most brides probably don't even know what a sixpence is, this part of the tradition is not used very often in modern times. However, if a bride would like to include it in her wedding, she can purchase a silver sixpence from many companies that sell bridal supplies such as garters(袜带) and invitations.