Explanation:

- Option 1: Two

- Most legal and formal documents require two witnesses for attestation.

- This is a common practice to ensure credibility.

- Option 2: One male-One female

- Typically, gender does not matter for witnesses.

- Legal documents usually just specify the number of witnesses.

- Option 3: Both male

- Again, gender is usually not a requirement for attestation.

- Having only male witnesses would not necessarily meet usual standards unless specified by a particular institution or country law.

- Option 4: Both female

- Similarly, the requirement for both witnesses to be female is uncommon and not generally necessary.