Explanation:
To determine the acidity of oxides, we need to analyze their chemical formula and structure.

As4O6:
This oxide contains arsenic (As) and oxygen (O) atoms. It has 4 arsenic atoms and 6 oxygen atoms. The chemical formula suggests that each arsenic atom is bonded to 1.5 oxygen atoms on average. This indicates that the oxide has a lower oxygen-to-arsenic ratio compared to As4O10.

As4O10:
This oxide also contains arsenic (As) and oxygen (O) atoms. It has 4 arsenic atoms and 10 oxygen atoms. The chemical formula suggests that each arsenic atom is bonded to 2.5 oxygen atoms on average. This indicates that the oxide has a higher oxygen-to-arsenic ratio compared to As4O6.

P4O10:
This oxide contains phosphorus (P) and oxygen (O) atoms. It has 4 phosphorus atoms and 10 oxygen atoms. The chemical formula suggests that each phosphorus atom is bonded to 2.5 oxygen atoms on average. This oxide has a similar oxygen-to-phosphorus ratio as As4O10.

P4O6:
This oxide also contains phosphorus (P) and oxygen (O) atoms. It has 4 phosphorus atoms and 6 oxygen atoms. The chemical formula suggests that each phosphorus atom is bonded to 1.5 oxygen atoms on average. This oxide has a lower oxygen-to-phosphorus ratio compared to P4O10.

Analysis:
The acidity of oxides is influenced by their ability to donate protons (H+) in aqueous solutions. Generally, oxides with a higher oxygen-to-metal ratio are more acidic because they can readily release protons.

Comparing the oxygen-to-metal ratios of the given oxides:
- As4O6 has the lowest oxygen-to-arsenic ratio (1.5:1)
- As4O10 and P4O10 have the highest oxygen-to-metal ratios (2.5:1)
- P4O6 has an intermediate oxygen-to-phosphorus ratio (1.5:1)

Conclusion:
As4O6 has the lowest oxygen-to-metal ratio among the given oxides, indicating that it is the least acidic. Therefore, option A is the correct answer.