单项选择题One of the characteristics that have made Mark Twain a major literary figure in the 19th century America is his use of ______.

单项选择题A linguist regards the changes in language and language use as ______.

单项选择题According to the law, children in Britain between the ages of should receive efficient fulltime education.

单项选择题Emerson based his religion on an intuitive belief in an ultimate unity, which he called ______.

单项选择题Which American president witnessed the disintegration of the Soviet Union and the Westernization of East European countries