Ans : Extention 
In windows, a(n) extension follows the file name and a period and indicates the file type.
        
             
        
        
        
Answer:
I am sure the answer is A
Explanation:
As you can see from the graph, the first time they pumped air, the numbers were 6, 1.2, and 2. Once they start pumping the numbers decrease. Therefore, I think the answer is A. It went to 5.7, 4, and 2 from 6, 1.2, and 2.1. 
 
        
             
        
        
        
Answer:
Combination of one or more columns used to identify particular rows in a relation is a key
 
        
             
        
        
        
Answer:
D. by using different background colors for different sections 
Explanation:
This can help people differentiate the different sections of your webpage. 
Hope this helps!
 
        
             
        
        
        
Answer:
You need to explain the entire network layout first.
Explanation:
Bringing on new IT Staff can be time consuming.  But depending on the possession you need to explain to them how the domain lay out is.