Observe to to gather facts, by paying close attention towards what you are working on. 
meanwhile, reference is the act or process on reaching to your conclusion, based on facts you already know .
        
             
        
        
        
What they have in common is that they both have the same number of atoms.
        
             
        
        
        
4.0 moles were used. hope ive helped you! please rate brailiest. :)
        
                    
             
        
        
        
Answer:
[NaCl]: 2M
Explanation:
This solution is made of NaCl therefore:
Our solute is NaCl
Moles of solute: 4
Our solution's volume is 2L
Molarity are the moles of solute contained in 1L of solution (mol/L)
[NaCl]: 4 mol /2L = 2M
We can also make a rule of three:
In 2 L we have 4 moles of solute
So, In 1 L we must have (1 . 4) /2 = 2 M