The right answer is D - mass. 
        
                    
             
        
        
        
Answer:
mole fraction of N_2 O = 0.330
mole of fraction SF_4 = 0.669
PRESSURE OF N_2 O = 39127.053 Pa
pressure of SF_4 = 792126.36
Total pressure   = 118253.413 Pa
Explanation:
Given data:
volume of tank 8 L
Weight of dinitrogen difluoride gas 5.53 g
weight of sulphur hexafluoride gas 17.3 g
Amount of 
amount of 
mole fraction of 
mole of fraction
PV = nRT
P of N_2 O 
mole of SF_4
Total pressure  = 39127.053 + 79126.36 = 118253.413 Pa
 
        
             
        
        
        
Explanation:
Atomic radius decreases from left to right in a period.
Therefore Calcium would have a smaller atomic size.
 
        
             
        
        
        
Explanation:
the solid substance which left on the filter paper is called Residue