Chlorine exists in two isotopic forms, Cl-37 and Cl-35, but its atomic mass is 35.5. This indicates the ratio of Cl-37 and Cl-35 is approximately
(a) 1 : 2
(b) 1 : 1
(c) 1:3
(d) 3:1
The answer is the option (c)
1:3 , because we know that chlorine is made up of two isotopes that have atomic masses of 35 u and 37 u in the ratio 1:3.