What is the angle of slope in tube settlers?

• A. 30‚àö√Ñ‚àö‚àÇ
• B. 60‚àö√Ñ‚àö‚àÇ
• C. 90‚àö√Ñ‚àö‚àÇ
• D. 180‚àö√Ñ‚àö‚àÇ