What is correct to say?

Options

A. Oxidation state of bromine varies from - 1to+ 6
B. Among `IO_4^(-) ClO_4^(-)` and `BrO_4^(-)`, the last one `(BrO_4^(-))` is the strongest oxldising agent
C. `HNO_3` is an oxidising agent
D. All are correct

Explanation

To answer the question regarding the oxidation states and the strongest oxidizing agents among the given options, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Oxidation States of Bromine:**
- The oxidation state of bromine can vary from -1 to +6. This is because bromine is a halogen, which can either gain an electron (to achieve a -1 state) or lose electrons (to achieve positive oxidation states).
- **Conclusion:** The statement about the oxidation state of bromine is correct.

2. **Identifying the Strongest Oxidizing Agent:**
- To determine which compound is the strongest oxidizing agent, we need to analyze the oxidation states of bromine in different compounds.
- For the compound \( \text{BrO}_4^- \):
- Let the oxidation state of bromine be \( x \).
- The equation for the oxidation state is: \( x + 4(-2) = -1 \) (because the overall charge is -1).
- Simplifying gives: \( x - 8 = -1 \) → \( x = +7 \).
- **Conclusion:** Bromine in \( \text{BrO}_4^- \) has an oxidation state of +7, indicating it is a strong oxidizing agent.

3. **Analyzing HNO3 as an Oxidizing Agent:**
- For \( \text{HNO}_3 \):
- The oxidation states are: H = +1, O = -2, and let nitrogen be \( x \).
- The equation is: \( +1 + x + 3(-2) = 0 \).
- Simplifying gives: \( +1 + x - 6 = 0 \) → \( x = +5 \).
- **Conclusion:** Nitrogen in \( \text{HNO}_3 \) has an oxidation state of +5, confirming it is also a strong oxidizing agent.

4. **Final Conclusion:**
- Since both \( \text{BrO}_4^- \) and \( \text{HNO}_3 \) are strong oxidizing agents, and the first statement about the oxidation states of bromine is correct, we conclude that all statements provided in the question are correct.
- **Final Answer:** The correct option is that all statements are correct.