An isotope of any element is the same, with a variation in the neutrons of the nucleus.
The mass number change but the atomic number doesn't.
In this case, protium, deuterium, and tritium are all hydrogen isotopes.
Protium is 1H or Hydrogen-1 is without neutrons.
Deuterium is 2H  or Hydrogen-2 has one neutron.
Tritium is 3H or Hydrogen-3 has two neutrons.
 
        
             
        
        
        
Answer:
B) geology; theory of continental drift
Explanation:
 
        
             
        
        
        
Sound intensity is the intensity/volume of sound. Frequency is how high or low the sound is.
        
                    
             
        
        
        
Answer:
A is the answer to the question