Identify A to C.
(a). An aqueous solution of a compoud (A) is acidic towards litmus and (A) is sublimed at about `300^@C`.
(b). (A) on treatment with an excess of `NH_4CNC` gives a red coloured compound (B) and on treatment with a solution of `K_4Fe(CN)_6` gives a blue coloured compound (C).

Explanation

To solve the given problem, we need to identify the compounds A, B, and C based on the information provided. Let's break down the steps:

### Step 1: Identify Compound A
- The question states that an aqueous solution of compound A is acidic towards litmus and that A sublimes at about 300°C.
- A common compound that fits this description is **Iron(III) chloride (FeCl₃)**.
- When dissolved in water, FeCl₃ dissociates to release HCl, making the solution acidic.

**Hint:** Look for a compound that is both acidic in solution and has a sublimation point around 300°C.
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