I believe the answer you are looking for is the 4th one.
Answer ; The question is missing in some details, but here are he details ;
The two naturally occurring isotopes of bromine are
81Br (80.916 amu, 49.31%) and
79Br (78.918 amu, 50.69%).
The two naturally occurring isotopes of chlorine are
37Cl (36.966 amu, 24.23%) and
35Cl (34.969 amu, 75.77%).
Bromine and chlorine combine to form bromine monochloride, BrCl.
Explanation:
The detaile calculation is as shown in the attachment.
Hydroxyl ions are OH⁻ while hydronium ions are H₃O⁺ which is essentially H⁺ ions. The formula for pH is: pH = -log[H⁺]. So, the greater the concentration of H⁺ is, the lower the pH which indicates acidity. On the other hand, the greater the concentration of OH⁻, the greater the pH which indicates basicity. This is also a consequence of the equation: pH + pOH = 14.
One is through sublimation, where the mixture is heated and iodine gets converted into gaseous form, leaving behind the iron fillings.
The other is to get a magnet near the mixture and all the iron fillings get attracted to it while iodine will be left over