Explanation:

- Option 1: Invalid consideration

- Forbearance to sue is generally not an invalid consideration. It involves a promise to refrain from exercising a legal right, which can be adequate consideration in a contract.

- Option 2: No consideration

- This is incorrect. Forbearance to sue involves giving up a legal claim or the opportunity to pursue one, which constitutes valid consideration.

- Option 3: Valid consideration

- Correct. Forbearance to sue is regarded as valid consideration as it involves a legal detriment by giving up a lawful right to litigate.

- Option 4: None of the above

- This would be incorrect since option 3 already correctly identifies forbearance to sue as valid consideration.