题目

Unique Tradition from UK Boxing Day     This holiday, which is observed on December 26, is a unique part of the Christmas season in Great Britain, as well as other Commonwealth nations. Boxing Day comes from a tradition that began in the Middle Ages more than 800 years ago. On this day, English churches would open their ‘alms box’ and distribute its contents to needy members of the community. It was also a day for servants to celebrate the holidays with their families, having usually worked the day before. Today, Boxing Day is one of the twenty-two paid holidays received by most workin关于声音的说法正确的是（   ）A．物体只要振动，人们就能听到声音B．声音只能通过介质传播C．声音在一切介质中的传播速度都是相同的D．声音中，人们听不见的声音只有超声波