1. Identify the given elements and their positions

The elements are:

• $\mathrm{Al}$, $\mathrm{In}$, $\mathrm{Tl}$ : Group 13
• $\mathrm{Ge}$, $\mathrm{Sn}$, $\mathrm{Pb}$ : Group 14

We need to find:

• the element with the highest first ionisation enthalpy
• the element with the lowest first ionisation enthalpy

Then state their most stable oxidation states, respectively.

2. Compare first ionisation enthalpies qualitatively

General trend

• Ionisation enthalpy generally decreases down a group.
• It generally increases across a period.

However, due to poor shielding by $d$ and $f$ electrons and the inert pair effect, there are irregularities in heavier elements.

Now compare the given elements:

Group 13

• $\mathrm{Al}$
• $\mathrm{In}$
• $\mathrm{Tl}$

Normally IE should decrease down the group, but $\mathrm{Tl}$ has unusually higher ionisation enthalpy than expected due to poor shielding by $4f$ electrons and lanthanide contraction. Still, among these, $\mathrm{Al}$ has high first IE.

Approximate trend: $\mathrm{In} < \mathrm{Tl} < \mathrm{Al}$

Group 14

• $\mathrm{Ge}$
• $\mathrm{Sn}$
• $\mathrm{Pb}$

Approximate trend: $\mathrm{Sn} < \mathrm{Pb} < \mathrm{Ge}$

Now comparing all six, the highest first ionisation enthalpy is for $\mathrm{Ge}$.

The lowest first ionisation enthalpy is for $\mathrm{In}$.

3. Find the most stable oxidation states

For $\mathrm{Ge}$

$\mathrm{Ge}$ is a Group 14 element. Its common oxidation states are $+2$ and $+4$, but the most stable for germanium is: $+4$

For $\mathrm{In}$

$\mathrm{In}$ is a Group 13 element. Its common oxidation states are $+1$ and $+3$. For indium, the most stable oxidation state is: $+3$

(Though inert pair effect increases down the group, it is strongest for $\mathrm{Tl}$; for $\mathrm{In}$, $+3$ remains the most stable.)

4. Match with the options

The required pair is: $+4 \text{ and } +3$

So the correct option is:

B: $+4$ and $+3$

5. Comparison with stored answer

Stored correct answer: B

My derived answer: B

So they agree.