Use periodic trend of oxides across Period 3

The given oxides are of Period 3 elements: $Al,\ Si,\ P,\ S$

Across a period from left to right, metallic character decreases and non-metallic character increases. Therefore:

• basic character of oxides decreases,
• acidic character of oxides increases.

Nature of each oxide

• $Al_2O_3$: amphoteric oxide, so it is the least acidic among these.
• $SiO_2$: weakly acidic oxide.
• $P_2O_3$ (more correctly $P_4O_6$): acidic oxide; it forms an acid with water, so it is more acidic than $SiO_2$.
• $SO_2$: strongly acidic oxide; it forms sulfurous acid in water: $SO_2 + H_2O \rightarrow H_2SO_3$ Hence it is more acidic than $P_2O_3$.

Arrange in increasing acid strength

Therefore, $Al_2O_3 < SiO_2 < P_2O_3 < SO_2$

Check options

• A: opposite trend, incorrect.
• B: $Al_2O_3 < SiO_2 < P_2O_3 < SO_2$ ✓
• C: places $SO_2$ less acidic than $P_2O_3$, incorrect.
• D: incorrect order.

Final answer

The correct option is B.