Give below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:

Assertion A: The stability order of +1 oxidation state of $\mathrm{Ga}$, In and $\mathrm{Tl}$ is Ga < In < Tl.

Reason R: The inert pair effect stabilizes the lower oxidation state down the group.

In the light of the above statements, choose the correct answer from the options given below:

<p>To evaluate the statements provided, let's first understand the concepts involved:</p> <p><b>Assertion A:</b> The stability order of the +1 oxidation state of $\mathrm{Ga}$, In, and $\mathrm{Tl}$ is Ga &lt; In &lt; Tl.</p> <p><b>Reason R:</b> The inert pair effect stabilizes the lower oxidation state down the group.</p> <p>The elements $\mathrm{Ga}$ (Gallium), $\mathrm{In}$ (Indium), and $\mathrm{Tl}$ (Thallium) belong to Group 13 of the periodic table. As we move down this group, the +3 oxidation state becomes less stable while the +1 oxidation state becomes more stable. This trend is attributed to the inert pair effect.</p> <p>The inert pair effect refers to the reluctance of the s-electrons to participate in bonding as we move down the group in the periodic table. For Group 13 elements, this effect causes the lower +1 oxidation state to be more stable compared to the +3 oxidation state down the group.</p> <p>Given this, the Reason R correctly explains why the +1 oxidation state is more stable for $\mathrm{Tl}$ compared to $\mathrm{Ga}$ and $\mathrm{In}$. Therefore, the stability order of the +1 oxidation state should indeed be Ga &lt; In &lt; Tl.</p> <p><b>Conclusion:</b> Both Assertion A and Reason R are true, and Reason R is the correct explanation for Assertion A.</p> <p>Therefore, the correct answer is:</p> <p><b>Option D:</b> Both A and R are true and R is the correct explanation of A.</p>