Answer = B = Neutrons and Mass Number
Isotopes are defined as those atoms which have same atomic number but different atomic masses.
Atomic mass is basically the number of protons and neutrons present in an atom.
Atomic number is the number of protons present in an atom.
So, in isotopes the number of protons are same but the number of neutrons vary due to which atomic masses also vary.
In given three isotopes, all have same number of protons but different number of neutrons.
i.e.
H-1 = 1 P + 0 N = 1 u (Proton)
H-2 = 1 P + 1 N = 2 u (Deuterium)
H-3 = 1 P + 2 N = 3 u (Tritium)
Hence, it is clear that the number after H shows a change in number of neutrons and mass number.
        
                    
             
        
        
        
Answer:
CO32−
Explanation:
We have to consider the valencies of the polyatomic ions involved. Recall that it is only a polyatomic ion with a valency of -2 that can form a compound which requires two sodium ions.
When we look closely at the options, we will realize that among all the options, only CO32− has a valency of -2, hence it must be the required answer. In order to be double sure, we put down the ionic reaction equation as follows;
2Na^+(aq) + CO3^2-(aq) ---------> Na2CO3(aq)
 
        
             
        
        
        
Answer:
C= 0.532M
Explanation:
The equation of reaction is 
H2SO4 + 2KOH = K2SO4+ H2O
nA= 1, nB= 2, CA= ?, VA= 48.9ml, CB= 1.5M, VB= 34.7ml
Applying 
CAVA/CBVB = nA/nB
(CA× 48.9)/(1.5×34.7)= 1/2
Simplify
CA= 0.532M
 
        
             
        
        
        
If people have children, If people die, and if there is a fire or volcanic eruption.
        
             
        
        
        
Answer:
A control group is someone who takes control over something so a tyrant or a dictator. 
Explanation:
If this isnt what your looking for let me know, there wasnt alot of context.