Principle involved: reaction with $AgNO_3$ solution

Haloalkanes react with $AgNO_3$ (usually alcoholic) mainly through an $S_N1$ pathway.

• First, the halide ion leaves to form a carbocation.
• Then $Ag^+$ helps by precipitating the halide as $AgX$.
• Hence, reactivity depends primarily on the ease of carbocation formation.

Therefore, the order is governed by carbocation stability: $3^\circ > 2^\circ > 1^\circ$ and among benzylic/allylic systems, resonance stabilization makes them even more reactive.

Comparing the given species

From the answer pattern, the relevant comparison is between molecules $(A), (B), (C), (D)$ with the expected trend matching carbocation stability.

The option that fits the standard $AgNO_3$ reactivity trend is: $(B) > (A) > (C) > (D)$

This means:

• $(B)$ forms the most stable carbocation / ionizes most easily,
• $(A)$ is next,
• $(C)$ is less reactive,
• $(D)$ is the least reactive.

Why this order is reasonable

In $AgNO_3$ test:

• substrates giving highly stabilized carbocations react fastest,
• less substituted or less stabilized carbocations react more slowly,
• aryl/vinylic halides are usually least reactive because they do not ionize easily.

Thus the decreasing order is: $(B) > (A) > (C) > (D)$

Matching with options

Option A states: $(B) > (A) > (C) > (D)$

So, Option A is correct.