Yogic Kriyas

Step 1: Understanding the Kriyas.
- (A) Sutra Neti: Sutra Neti is a nasal cleansing practice, but it does not specifically target the digestive tract.
- (B) Nauli: Nauli is a yogic technique that involves massaging the abdominal muscles, which helps to remove toxic material from the digestive tract and improve digestion. It is specifically effective for the stomach, liver, and intestines.
- (C) Trataka: Trataka is a meditation technique and does not have a direct effect on detoxifying the digestive system.
- (D) Yog Mudra: Yog Mudra is a posture that helps to calm the mind and body but does not specifically target the detoxification of the digestive system.

Step 2: Conclusion.
Therefore, the correct answer is (B) Nauli, as it helps in removing toxins from the digestive tract.

Final Answer: (B) Nauli.

Step 1: Understanding the Kriyas.
- (A) Sheetali: Sheetali is a breathing technique that cools the body but does not specifically improve eyesight.
- (B) Neti: Neti is a nasal cleansing technique, which clears the sinuses, but does not directly affect eyesight.
- (C) Kapalbhati: Kapalbhati is a breathing exercise that benefits the respiratory system but is not primarily focused on improving eyesight.
- (D) Trataka: Trataka is a meditation technique that involves focusing on a single point, typically a flame, to improve concentration and strengthen the visual mechanism. It is well-known for its benefits in improving eyesight and calming the mind.

Step 2: Conclusion.
Thus, the correct answer is (D) Trataka, as it specifically improves eyesight and tones up the visual mechanism.

Final Answer: (D) Trataka.