表示问题的英文单词有哪些

1. Problem 2. Issue 3. Challenge 4. Concern 5. Dilemma 6. Obstacle 7. Complication 8. Difficulty 9. Conflict 10. Concern 11. Crisis 12. Disturbance 13. Frustration 14. Headache 15. Problematic 16. Troublesome 17. Complicating 18. Complex 19. Troubling 20. Dispute