Which element of Group 17 has two isotopes of masses 35 and 37 amu with average abundance of 75.77% and 24.23%, respectively?

Correct option is A

The correct answer is (a) Chlorine
 Chlorine belongs to Group 17 (also called the halogens) of the periodic table.
 Chlorine has two naturally occurring isotopes: chlorine-35 (35Cl) and chlorine-37 (37Cl).
 Chlorine has the atomic number 17 and the chemical symbol Cl. Chlorine was discovered in 1774 by extracting it from hydrochloric acid.
 The halogens are located on the left of the noble gases on the periodic table.
 These five toxic, non-metallic elements make up Group 17 of the periodic table and consist of: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).
 Halogens form diatomic molecules (of the form X2​, where X denotes a halogen atom) in their elemental states.