We may find that learning a foreign language does not have to be________learning our mother tongue,but can in fact be twice ________.
In the past decades, sea ice _____in the Arctic as a result of global warming.
In our country the cold weather in the north_____ sharply _____the hot weather in the south.
_____of danger in the street at night, she had to go home, with a friend_____ her.
I don't doubt _____ he will pass the exam.
The problem of global warming is serious. _____ , the sea levels have _____a little.