Q: 16 (CDS-I/2017)

There are two elements—calcium (atomic number 20) and argon (atomic number 18). The mass number of both the elements is 40. They are therefore known as
question_subject: 
Logic/Reasoning
question_year: 
2017
question_exam: 
CDS-I
stats: 
0,32,176,48,24,104,32