The word bird used to mean "young bird"; today it means "any kind of bird". This is called ______ in terms of semantic change.

单项选择题Which of the following is NOT of British origin

单项选择题Generally speaking, the eastern American cities are (more) ______ than the western ones.

单项选择题One of the most promising methods of storing hydrogen fuel is ______.

单项选择题Which of the following is the characteristic of hydrogen

单项选择题It can be inferred from the passage that the Sun’s light travels ______.