Arrange the following oxides in the increasing order of their basic strength:

(A) $V_2O_5$
(B) $V_2O_3$
(C) $V_2O_4$
(D) $Mn_2O_7$

Choose the correct answer from the options given below:

(D), (A), (C), (B)

The correct answer is Option (1) → (D), (A), (C), (B)

Basic strength of metal oxides decreases as the oxidation state of the metal increases.
High oxidation state oxides are acidic, low oxidation state oxides are basic, and intermediate ones are amphoteric.

Let us analyze each oxide:

• Mn₂O₇ → Mn in +7 oxidation state → strongly acidic
• V₂O₅ → V in +5 oxidation state → acidic
• V₂O₄ → V in +4 oxidation state → amphoteric
• V₂O₃ → V in +3 oxidation state → basic

So, increasing order of basic strength (least basic → most basic):

$\text{Mn}_2\text{O}_7 < \text{V}_2\text{O}_5 < \text{V}_2\text{O}_4 < \text{V}_2\text{O}_3$

(D), (A), (C), (B)