Explanation:

- Option 1: law

- This means only the strict legal rules govern cases related to specific performance of a contract.

- Option 2: equity

- Here, only principles of fairness, or what is just and equitable, guide the judgment.

- Option 3: equity and law

- This means both legal rules and principles of fairness are applied together. In specific performance cases, courts often use both, considering not just the strict law but also fairness in the situation.

- Option 4: neither equity and nor law

- This implies decisions are made on some other basis, not using law or equity, which is incorrect.

The correct answer is: Option 3 ("equity and law").

Specific performance is an equitable remedy, meaning both legal rights and principles of fairness are applied. Courts do not rely strictly on law alone.