He set a giant boulder at the mouth of the cave.
        
             
        
        
        
<span>Ishmael Beah was able to learn about the existence of the Sierra Leone Civil War because of the dispute on his outpost. He was a very renowned author or several items including: (1) A long way gone, and (2) Memoirs of a Boy Soldier, and (3) Radiance of Tomorrow. His works were published in several languages. </span>
        
                    
             
        
        
        
Answer:
The answer is B: Scientists are confused by the different ways the rocks move, and the theories involving wind, ice, and mud have not been proven.
Explanation:
In the second paragraph, it is said that scientists have been baffled by the variety of rock movement. Then, there was a description of their movement and some possible reasons for why it happens. Some of the reasons(wind, ice and mud) were suggested by scientists. The paragraph then ends by saying that none of the theories have been confirmed by research. 
This is conveyed very well by option B therefore it the correct option as the main idea of the paragraph.
 
        
             
        
        
        
The correct answer is B. Instructs us to greet friends and acquaintances with warmth and respect,
Hope this helps! :)