The correct answer is - the release of methane from thawed permafrost.
In the past decade it has been noticed that the levels of methane are increasing in the atmosphere, and the biggest ''producer'' of this methane is the melting permafrost. There's huge amounts of methane trapped underground bellow the permafrost. But the permafrost is melting because of the global worming, so the methane is free to come out and go up in the atmosphere. 
        
             
        
        
        
Answer:
They are called covalent bonds. 
Explanation:
I just went through the lesson.
 
        
                    
             
        
        
        
The theory of Continental Dift
        
             
        
        
        
<h2><em>what is the main theme in reproduction.</em></h2>
- <em>The five central themes of biology are</em><em> </em><em><u>structure and function of cells, interactions between organisms, homeostasis, reproduction and genetics, and evolution</u></em>
<em>hope </em><em>it</em><em> helps</em>
<em>#</em><em>c</em><em>a</em><em>r</em><em>r</em><em>y</em><em> </em><em>on</em><em> learning</em>
<em>follow</em><em> me</em><em> and</em><em> mark</em><em> me</em><em> as</em><em> brainlist</em><em> plss</em>