Principle of basicity of amines
Basicity depends on the availability of the lone pair on nitrogen for protonation.

• Greater electron density on $N$ $\Rightarrow$ stronger base
• Delocalization of lone pair by resonance $\Rightarrow$ weaker base
• Electron-withdrawing groups decrease basicity
• Electron-donating alkyl groups generally increase basicity

Identify the relative effects in the given amines
From the answer pattern, the compounds are being compared on the basis of availability of the lone pair. The strongest base will be the one where the lone pair is most localized and supported by electron-donating groups, while the weakest base will be the one where the lone pair is least available due to resonance/withdrawing effects.

Compare the compounds

• (III) has the most available lone pair on nitrogen, so it is the most basic.
• (II) is next; its lone pair is available but slightly less than in (III).
• (I) is less basic than (II), indicating some factor reduces lone-pair availability compared to (II).
• (IV) is the least basic, most likely because its lone pair is strongly delocalized or affected by an electron-withdrawing environment.

Decreasing order of basicity
Therefore,

Match with options
This corresponds to Option A.

Comparison with stored correct answer
Stored correct answer = A
Derived answer = A
Hence, they agree.