Among the following, a pair of compound and an element respectively is

Options

A. iron powder, rust powder.
B. rust powder, iron powder.
C. lime, rust powder.
D. rust powder, lime.

Explanation

To solve the question of identifying a pair of a compound and an element from the given options, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Element**: A substance that cannot be broken down into simpler substances by chemical means. It consists of only one type of atom.
- **Compound**: A substance formed when two or more different elements are chemically bonded together. It has a fixed composition and properties that differ from the individual elements.

2. **Identify the Given Substances**:
- The substances mentioned in the transcript are iron powder (Fe) and rust powder (FeO).
- Iron powder (Fe) is an element because it consists of only iron atoms.
- Rust powder (FeO) is a compound because it consists of iron and oxygen atoms chemically bonded together.

3. **Determine the Pair**:
- From the definitions, we can conclude that:
- **Element**: Iron powder (Fe)
- **Compound**: Rust powder (FeO)

4. **Select the Correct Option**:
- The question asks for a pair of a compound and an element respectively. Based on our identification:
- The correct pair is: Rust powder (FeO) as the compound and Iron powder (Fe) as the element.

5. **Final Answer**:
- Therefore, the answer is option number two, which states that the pair consists of rust powder (FeO) as the compound and iron powder (Fe) as the element.