A radioactive element A decays by the sequence and with halflives given below: Which of the following statements about this system are correct? 

a) 
The mass number of B is greater than A 
b) 
After two hours, less than 10% of the initial A is left 
c) 
Maximum amount of B present at any time is less than 50% of the initial amount of A 
d) 
The atomic numbers of A and C are the same 
A radioactive element A decays by the sequence and with halflives given below: Which of the following statements about this system are correct? 

a) 
The mass number of B is greater than A 
b) 
After two hours, less than 10% of the initial A is left 
c) 
Maximum amount of B present at any time is less than 50% of the initial amount of A 
d) 
The atomic numbers of A and C are the same 
(b,d) 2 hours = 4 half lives, therefore, amount left = 6.25% of original. Loss of one particles does not change the atomic number 