Heaters should be kept going in the night for men to survive in polar areas.

• A、True
  
  

• B、False
  
  

• C、Not Given
  
  

As discovered by expedition scientists, Antarctica has not always been so cold as it is today, so has the Arctic.

• A、True
  
  

• B、False 
  
  

• C、Not Given
  
  

Task 1

16.Paragraph       ①      

17.Paragraph      ③        

18.Paragraph      ④    

19.Paragraph      ⑥                

20.Paragraph      ⑦     

A. Soot's Role in Climate Changes Above Oceans and Land

B. Observations of Warming in the Northern Hemisphere

C. Explanation of Increased Warming Effect Caused by Soot

D. Black Soot in Snow and Icy Areas Leading to Climate Change

E. Black Soot Contributing to Global Warming

F. Greenhouse Gases as the Main Factor of Global Warming