Read the following and answer any four questions
When a silvery grey powder of a solid (A) is mixed with a powder of solid (B) no reaction occurs. But if the mixture is ignited and lighted using magnesium ribbon a reaction occurs with evolution of large amount of heat forming product (C) which settles down as liquid metal and the solid product (D) formed floats on the liquid (C). (C) in solid form reacts with moisture to form rust. The amount of heat generated during the reaction is so high that the reaction is used in welding of electric conductors, joints in railway tracks. Based on this information, Identify A and C?

Options

A. A-Al and C-Fe
B. A-Fe and C-Al
C. A-Mg and C-Al
D. A-Al and C-Cu

Explanation

To solve the question, we need to identify the substances A and C based on the information provided.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- We have two solids, A and B. When mixed, they do not react until ignited with a magnesium ribbon.
- The ignition leads to a reaction that produces a large amount of heat.

2. **Identifying Product C**:
- The problem states that product C settles down as a liquid metal and that it reacts with moisture to form rust.
- Rust is typically known as iron(III) oxide, which can be represented as Fe₂O₃·xH₂O.

3. **Determining the Metal**:
- Since product C is a metal that can form rust, it is likely to be iron (Fe).
- Therefore, we can conclude that C is iron (Fe).

4. **Identifying Solid A**:
- The problem describes solid A as a silvery grey powder that does not react with solid B until heated.
- Given that aluminum (Al) is a silvery grey metal and can react with iron(III) oxide (rust) to produce iron and aluminum oxide, we can deduce that solid A is aluminum (Al).

5. **Final Identification**:
- Thus, we identify:
- Solid A: Aluminum (Al)
- Product C: Iron (Fe)

### Summary of Findings:
- **A** is Aluminum (Al).
- **C** is Iron (Fe).