Explanation:

- Hardship refers to severe suffering, deprivation, or difficult conditions.

- Option 1: Mystery involves something that is not understood or is perplexing. This does not align with the idea of suffering or difficulty.

- Option 2: Misery relates to a state of great discomfort or distress, often due to poverty or adversity. It matches well with the notion of hardship.

- Option 3: Difficult refers to something that is not easy to do or understand. While partly similar, it doesn't capture the suffering aspect of hardship.

- Option 4: Privacy is the state of being free from public attention. It does not relate to hardship.