1. Write the equilibrium reaction

$Fe_2O_3(s) + 3CO(g) \rightleftharpoons 2Fe(l) + 3CO_2(g)$

2. Apply Le Chatelier’s principle

Le Chatelier’s principle says that if a system at equilibrium is disturbed, it shifts in a direction that opposes the disturbance.

3. Important fact about pure solids and liquids

In a heterogeneous equilibrium, the activities of pure solids and pure liquids are taken as constant. So:

• $Fe_2O_3(s)$ does not appear in the equilibrium expression.
• $Fe(l)$ also does not appear in the equilibrium expression.

Thus, the equilibrium constant expression is

$K = \frac{(P_{CO_2})^3}{(P_{CO})^3}$

Only the gaseous species affect the equilibrium position.

4. Check each option

Option A: Removal of $CO$

Removing a reactant gas decreases $CO$. The system will try to produce more $CO$, so equilibrium shifts to the left.

So, this disturbs the equilibrium.

Option B: Removal of $CO_2$

Removing a product gas decreases $CO_2$. The system will try to form more $CO_2$, so equilibrium shifts to the right.

So, this disturbs the equilibrium.

Option C: Addition of $CO_2$

Adding a product gas increases $CO_2$. The system will try to consume $CO_2$, so equilibrium shifts to the left.

So, this disturbs the equilibrium.

Option D: Addition of $Fe_2O_3$

$Fe_2O_3$ is a solid. Changing the amount of a pure solid does not change the equilibrium position, provided some solid is already present.

So, this will not disturb the equilibrium.

5. Final answer

The option that will not disturb the equilibrium is:

$\boxed{D}$