单选题：根据以下资料，回答 题：Experts say over half of the world’s seven thou

根据以下资料，回答 题：
Experts say over half of the world’s seven thousand languages are in danger of disappearing．Every two weeks one language disappears.
Sometimes a language disappears immediately when the last person speaking it dies．Or, a local language might disappear more slowly．This happens when an official language is used more often and children stop learning the local language of their parents．Official languages often represent a form of control over a group of people.
Throughout history, the language spoken by a powerful group spreads across a civilization．The more powerful culture rarely respects the language and culture of smaller groups．Smaller cultures lose their local language as the language of the culture in power has a stronger influence．
Experts say protecting languages is very important for many reasons．Languages contain the histories, ideas and knowledge of a culture．Languages also contain valuable information about local medicines, plants and animals．
Many endangered languages are spoken by native cultures in close contact with the natural world．Their ancient languages contain a great deal of information about environmental systems and species of plants and animals that are unknown to scientists．As the last speakers of a language die off, the valuable information carried within a language also disappears．Language is, in many ways, a window to the mind and the world．
Any hope for protecting languages can be found in children and their willingness to learn．It is these young people who can keep this form of culture alive for future generations.

Which of the following is true? A．No one can prevent languages from disappearing.
B．There will not be any local languages left some day.
C．There have existed 7,000 languages in history.
D．Half of the world’s languages will possibly disappear.