The molecularity of the complex reaction is determined by the number of the molecules taking part in the reaction.

It is important that :--> Order of reaction and molecularity of reaction are rarely equal to or greater then three.

So, here right answer is (6+2) = 8 ...ans...

$$Hope it's help... $$

Molecularity refers to the number of molecules or ions participating as reactants in an elementary reaction. In order to determine the molecularity of the given reaction, we need to analyze the reaction mechanism.

The reaction given, 6KI + 2FeCl3 → 2FeI3 + 6KCl + I2, can be considered to occur in multiple steps. Let's break it down:

Step 1: Formation of FeI3
In this step, the reaction between FeCl3 and KI takes place. One FeCl3 molecule reacts with three KI molecules to form FeI3 and three KCl molecules.
FeCl3 + 3KI → FeI3 + 3KCl

Step 2: Formation of KI and I2
In this step, FeI3 reacts with excess KI to form KI and I2.
FeI3 + 3KI → 3KCl + I2

From the reaction mechanism, it is evident that the reaction occurs in two steps. But, it is important to note that the molecularity is determined by the slowest step in the reaction mechanism.

In this case, the first step is the slowest step as it involves the reaction between one FeCl3 molecule and three KI molecules. Therefore, the molecularity of the given reaction is determined by the reactants involved in the slowest step, which is the first step.

The first step involves one FeCl3 molecule and three KI molecules, giving a total of four molecules participating as reactants. Hence, the molecularity of the given reaction is 4.

Therefore, the correct option is (4) 2.

To summarize:
- The reaction occurs in two steps.
- The molecularity is determined by the slowest step.
- The first step involves one FeCl3 molecule and three KI molecules, giving a total of four molecules participating as reactants.
- Therefore, the molecularity of the given reaction is 4.