21. What is the minimum distance for clear vision? A) 10 cm B) 20 cm C) 25 cm 22. The frequency of alternating current for home appliances is D) infinite A) 60 Hz B) 100 Hz C) 220 Hz 23. Operation flood in India known for B) Milk Production D) Kargil war A) Flood outbreak C) Sugarcane production 24. El Nio effect is defined as A) Prolonged warming in the Pacific Ocean sea surface temperatures B) Heavy snow fall C) High temperature in tropical region D) All the above D) 50 Hz 25. Choose the correct alternative in place of question mark, 1, 5, 13, 25, 41, ? A) 51 B) 57 C) 61 D) 63