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The priorities are assigned to different substituents while finding an E and Z isomer.

If the two higher priority groups are on the same side of the double bond, then they are called Z-isomers and if the two higher priority groups are on the trans side of the doubly bonded atoms then they are termed E-isomer.

The highest priority among the substituents goes to the one with the highest atomic number, i.e., the atoms that are bonded directly to thecarbons.

Therefore, the greater the atomic number, the higher the priority assigned to the substituent.

As iodine has a higher atomic number than bromine, hence, the highest priority is assigned to iodine.

The order of assigning the relative priorities is

-I > -Br > -OH > -CH₃

Here, iodinehas the highest atomic number, then bromine, then oxygen, and at last thecarbon atom.

As thehighest priority among the substituents goes to the one with the highest atomic number,therefore the atoms that are bonded directly to thecarbons.

Here, oxygenhas the highest atomic number, the rest compounds have carbon in each.

Now, while assigning the priorities look for the second atom bonded to carbon. For this, the carbon attached to chlorine will have second priority.

The later priority goes to carbon bonded with another carbon through double bond and at last the carbon bonded with another carbon through a single bond.

- CH=CH₂ > -C- C- OH

H H₂ H₂

Therefore, the correct order of assigning the relative priorities is

-OH > -CH₂Cl >- CH=CH₂ > -CH₂CH₂COH