Answer: C) 8 Explanation: Let the number of boys = x From the given data, => [21x + 16(18)]/(x+16) = 19 => 21x - 19x = 19(16) - 16(18) => 2x = 16 => x = 8 Therefore, the number of boys in the class = 8.

Answer: D) Odontology Explanation: The study or scientific study of the structure, development, and abnormalities of the teeth is called Odontology. The science that studies teeth and their surrounding tissues, especially the prevention and cure of their diseases is called Dentology.

Answer: A) Geothermal Energy Explanation: Geothermal energy is heat energy generated and stored in the Earth. Geothermal energy has been used for thousands of years in some countries for cooking and heating. It is simply power derived from the Earth's internal heat.

Answer: D) All the above Explanation:

Answer: A) Capillary action phenomenon Explanation: Blotting paper absorbs ink by the process of capillary action. The capillary action is based on the property of surface tension of liquid.   All unsized paper will absorb water. Blotting paper is not sized and made bulkier to provide capillary action for faster absorption of liquid.   Blotting paper has also been sold as a cosmetic to aid in the removal of skin oils and makeup.

Answer: D) TIANHE 2 --- CHINA Explanation:

Answer: D) 8 Explanation: 9321 = 3 x 13 x 239 = 31 x 13 1 x 239 1 ; add one to all the powers ie., (1+1) x (1+1) x (1+1)= 8 ; we get eight factors.

Answer: B) स्ट्रोंटियम व्याख्या: हम जानते हैं कि आवर्त सारणी के एक ही समूह के तत्वों में समान विशेषताएं होती हैं। यहाँ मैग्नीशियम और स्ट्रोंटियम ने कुछ समान गुण साझा किए क्योंकि वे दोनों एक ही समूह के हैं। Sr स्ट्रोंटियम का रासायनिक प्रतीक है जो एक समूह दो तत्व है; इसका परमाणु क्रमांक 38 है।