选出正确的字

①乡音无改鬓毛（衰  哀）____。

②笑问客从（何  河）____处来。

在5月17日世界电信日到来之际，我市移动、联通和电信三大通信公司均为客户推出了3G业务，通过3G网络可提供无线视频通话、无线上网等多项服务．这些服务是通过____ （选填“超声波”、“次声波”或“电磁波”）来传递信号的，它在真空中的传播速度约为____ m/s．

       Do you still get free plastic bags from the supermarkets? Things have changed.
       China has banned（禁止）free plastic bags in  shops and supermarkets，and people have to pay for using plastic bags. The rule started on June 1st. It came because our country tried to make less litter. Making super-thin plastic bags has also been banned.
       The Chinese once used about 3,000,000,000 plastic shopping bags a day，and they have caused pollution of the environment. The bags have become a main cause of plastic pollution because they are easy to break and people throw them away here and there. So the Chinese people are encouraged to bring their own bags for shop ping.
       What kind of shopping bag is the best to bring? Some students in Chongqing have a good idea. They make their own shopping bags. They use old clothes to make cloth bags，and send them to their parents as presents. They also ask their parents and friends to use cloth bags instead of plastic ones. They think it is their duty to protect the environment.
根据短文内容，选择最佳答案。