Is it true that in nature, chlorine exists in two isotopic forms, with masses of 35 u and 37 u in a 3:1 ratio?

The given statement is true.

There are two isotopes of chlorine Cl– 35 and Cl – 37. The mass of chlorine Cl-35 isotopes is 35u and its abundance in nature is 75%, while the mass of chlorine Cl-37 isotope is 37u, and its abundance in nature is 25%.  This means chlorine exists in two isotopic forms, with masses of 35 u and 37 u in a 3:1 ratio.