Answer:
1)
2)
3)
4)
Step-by-step explanation:
We have the substituents:
a)
b)
c)
d)
If we remember that Cahn-Ingold-Prelog rules the highest priority is given by the atomic number. Therefore the highest priority is "Cl" (an atomic number equal to 17), the next one is "OH" due to the oxygen (an atomic number equal to 8). For c) and d) we have a carbon bonded to the chiral carbon, therefore we have to check the next atom. The difference between c) and d) are the "O" and "S" atoms, the atom with the highest atomic number is "S" (an atomic number equal to 16) therefore the highest priority is for d) and then c). So finally, the priority is:
1)
2)
3)
4)
I hope it hepls!