Which of the following is used for dissolution of gold?
(a) Hydrochloric acid (b) Sulphuric acid
(c ) Nitric acid ,(d) Aqua regia

Explanation

To solve the question "Which of the following is used for dissolution of gold?" we need to analyze the options provided:

1. **Understanding the Options**:
- (a) Hydrochloric acid
- (b) Sulphuric acid
- (c) Nitric acid
- (d) Aqua regia

2. **Analyzing Each Option**:
- Hydrochloric acid (HCl) is a strong acid but is not capable of dissolving gold on its own.
- Sulphuric acid (H2SO4) is also a strong acid but does not dissolve gold.
- Nitric acid (HNO3) can dissolve some metals but does not dissolve gold by itself.
- Aqua regia, which is a mixture of concentrated hydrochloric acid and concentrated nitric acid, is known for its ability to dissolve noble metals like gold.

3. **Conclusion**:
- Among the options provided, the only one that is used for the dissolution of gold is **(d) Aqua regia**.

### Final Answer:
**(d) Aqua regia**