To analyze the statements regarding group 13 elements' oxides, let's consider each one in detail:
### Statement I: Boron trioxide is acidic.
- **Explanation**: Boron trioxide (\( \text{B}_2\text{O}_3 \)) is indeed acidic. When it reacts with water, it forms boric acid (\( \text{H}_3\text{BO}_3 \)), which is a weak acid. Therefore, this statement is **true**.
### Statement II: Oxides of aluminium and gallium are amphoteric.
- **Explanation**: Aluminium oxide (\( \text{Al}_2\text{O}_3 \)) and gallium oxide (\( \text{Ga}_2\text{O}_3 \)) are both amphoteric. They can react with both acids and bases. For instance, \( \text{Al}_2\text{O}_3 \) can react with hydrochloric acid (\( \text{HCl} \)) to form aluminium chloride (\( \text{AlCl}_3 \)), and with sodium hydroxide (\( \text{NaOH} \)) to form sodium aluminate. Therefore, this statement is also **true**.
### Statement III: Oxides of indium and thallium are basic.
- **Explanation**: Indium oxide (\( \text{In}_2\text{O}_3 \)) tends to be amphoteric, not strictly basic. Thallium oxide (\( \text{Tl}_2\text{O}_3 \)) is generally considered more basic but can also show amphoteric behavior. Therefore, this statement is **partially true**, but not entirely accurate, as it does not cover the full nature of both oxides.
### Conclusion
- Statement I is **true**.
- Statement II is **true**.
- Statement III is **false** in its strong assertion that both oxides are basic.
Thus, the correct answer is **(D) (I) and (II) only**.
