Answer: D) Covalent bonds Explanation: Deoxyribose, which is a pentose, and a phosphate group are the two molecules together form the two sides of the DNA i.e, A sugar (deoxyribose) and a phosphate. DNA is a double-stranded molecule twisted into a helix (think of a spiral staircase). Each spiraling strand, comprised of a sugar-phosphate backbone and attached bases, is connected to a complementary strand by non-covalent hydrogen bonding between paired bases. The bases are adenine (A), thymine (T), cytosine (C) and guanine (G). A and T are connected by two hydrogen bonds. G and C are connected by three hydrogen bonds.

Answer: A) Rs. 620 Explanation: Let the C.P of one item is Rs. P and that of other is Rs. (7500 - P) According to the data given C.P = S.P => Px(116/100) + (7500-P)x(86/100) = 7500 => 30P = 105000 => P = 3500 Required difference between selling prices = Rs. [(3500/100) x 116] - [(4000/100) x 86] = 4060-3440 = Rs. 620

Answer: A) Lactic acid Explanation:

Answer: B) North Explanation: The azimuth originates at true North i.e, the azimuth originates from the north point. It is a measure of how far an object forms the observer's north point.   Azimuth is a technical mapping term which is used to describe the direction of an angle between north and south on a compass circle through which the circle line passes. It is the most common military method to express direction. When using an azimuth, the point from which the azimuth originates is the center of an imaginary circle.

Answer: A) Stratification Explanation: Stratification as actually the settling down of sediments with different properties to form layers/strata over years. Stratification especially occurs on the bed of water bodies such as oceans.   Stratified sedimentary rocks are used to study the ecological conditions over previous years/eras.     The other choices like Windstorms, Glacial Ice and Stream water are mediums which sediments are transported.

Answer: D) 437 Explanation: The series follow the rule,   21 = 77 = 92-4165 = 132-4285 = 172-4 5,9,13,17,21,(+4)...In the same way next no. will be 212-4 = 441 - 4 = 437

Answer: A) 226.65 Explanation: 55.55 + 155 + 15.55 + 0.5 + 0.05 = ?    55.55 155.00  15.55    0.5    0.05 _______ 226.65 _______   Hence, the value of the given equation 55.55 + 155 + 15.55 + 0.5 + 0.05 = 226.65.

Answer: A) the existence of unpaired electrons in the valence shell Explanation: When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.   Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.