A' on heating at `700^(@)C` in air gives a white infusible amorphous powder (B) which is decomposed when heated in the currect of steam to give white powder 'C' and a gas 'D'.'D' turns red litmus blue and in aqueous solution , gives reddish brown ppt with `K_(2)HgI_(4)`. compound 'C on strong heating gives 'E.
'E' is

Options

A. `B_(2)O_(3)`
B. `SiO_(2)`
C. `NH_(3)`
D. `N_(2)O`

Explanation

To solve the problem step by step, we need to identify the compounds A, B, C, D, and E based on the information provided.

### Step 1: Identify Compound A
- **Given**: Compound A on heating at `700°C` in air produces a white infusible amorphous powder (B).
- **Analysis**: A common compound that fits this description is **silicon (Si)**. When silicon is heated in air, it forms silicon dioxide (SiO₂), which is a white infusible powder.

### Step 2: Identify Compound B
- **From Step 1**: We identified that B is likely **silicon dioxide (SiO₂)**.

### Step 3: Identify Compound C and Gas D
- **Given**: Compound B (SiO₂) is decomposed when heated in the current of steam to give white powder C and gas D.
- **Analysis**: When silicon dioxide reacts with steam, it forms silicon monoxide (SiO) as the white powder (C) and hydrogen gas (H₂) as the gas (D).
- **Gas D**: Hydrogen gas turns red litmus blue, confirming it is a basic gas.

### Step 4: Identify the Reaction of Gas D
- **Given**: Gas D (H₂) gives a reddish-brown precipitate with `K₂HgI₄`.
- **Analysis**: The reddish-brown precipitate formed with `K₂HgI₄` is indicative of the formation of **mercury(I) iodide (Hg₂I₂)**, which confirms that D is indeed hydrogen.

### Step 5: Identify Compound E
- **Given**: Compound C (SiO) on strong heating gives E.
- **Analysis**: When silicon monoxide is heated strongly, it can further decompose to form silicon (Si) and carbon monoxide (CO). However, since we are looking for a compound, the most relevant product here is **silicon (Si)**.

### Conclusion
- **E** is **silicon (Si)**.

### Final Summary of Compounds
- A: Silicon (Si)
- B: Silicon dioxide (SiO₂)
- C: Silicon monoxide (SiO)
- D: Hydrogen gas (H₂)
- E: Silicon (Si)