`"Colemanite" + Na_(2)CO_(3) overset("Fused")rarr (A) + (B) + CO_(2)`
`underset("Solution")((A)) + CO_(2) rarr(B) + Na_(2) CO_(3)`
`(B) + conc HCl rarr NaCl + underset("Acid")((C))`
`underset("Acid")((C)) +H_(2)O rarr underset("Acid")((D))`
`(D) overset("Strong heating")rarr (E)`
`(E) +CuSO_(4) overset("Heated") underset("inflame")rarr underset("Blue-coloured compound")((F))`.
Compound `(D)` is.

Options

A. `H_(2)B_(4)O_(7)`
B. `HBO_(2)`
C. `H_(3)BO_(3)`
D. `H_(2)O`

Explanation

To solve the problem step by step, we will follow the reactions provided and identify compound (D).

### Step 1: Reaction of Colemanite with Sodium Carbonate
**Reaction:**
\[ \text{Colemanite (Ca}_2\text{B}_6\text{O}_{11}) + \text{Na}_2\text{CO}_3 \xrightarrow{\text{Fused}} (A) + (B) + \text{CO}_2 \]

**Products:**
- (A) = Sodium Metaborate \((\text{NaBO}_2)\)
- (B) = Sodium Tetraborate \((\text{Na}_2\text{B}_4\text{O}_7)\)
- \(\text{CO}_2\) is also produced.

### Step 2: Reaction of (A) with CO2
**Reaction:**
\[ (A) + \text{CO}_2 \rightarrow (B) + \text{Na}_2\text{CO}_3 \]

**Products:**
- (B) = Sodium Tetraborate \((\text{Na}_2\text{B}_4\text{O}_7)\)

### Step 3: Reaction of (B) with Concentrated HCl
**Reaction:**
\[ (B) + \text{conc HCl} \rightarrow \text{NaCl} + (C) \]

**Products:**
- (C) = Tetraboric Acid \((\text{H}_2\text{B}_4\text{O}_7)\)

### Step 4: Reaction of (C) with Water
**Reaction:**
\[ (C) + \text{H}_2\text{O} \rightarrow (D) \]

**Products:**
- (D) = Boric Acid \((\text{H}_3\text{BO}_3)\)

### Step 5: Strong Heating of (D)
**Reaction:**
\[ (D) \xrightarrow{\text{Strong heating}} (E) \]

**Products:**
- (E) = A product that can further react with CuSO4.

### Step 6: Reaction of (E) with CuSO4
**Reaction:**
\[ (E) + \text{CuSO}_4 \xrightarrow{\text{Heated}} (F) \]

**Products:**
- (F) = Blue-coloured compound (likely a copper borate).

### Conclusion
The compound (D) is **Boric Acid** \((\text{H}_3\text{BO}_3)\).

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