I have the quiz and I'm having a problem choosing the right option for this question can you please help?

Q1/ Under the Fair Work Act, you can terminate a person's employment for:?

1. Temporary absence from work because of illness or injury
2. Trade union membership or participation in trade union activities outside of working hours or, with the employer's consent, during work hours
3. Non-membership of a trade union
4. Seeking office or acting as a representative of employees
5. Filing a complaint or participating in proceedings against an employer involving alleged breaches of law or regulations
6. None of the above