Answer: B) 13 years Explanation: Given R + S + M + D = 76 => R+7 : S+7 : M+7 : D+7 = 7:6:5:8 => Let the ratio = x => M+7 = 5x => M = 5x-7 => R = 7x-7 => S = 6x-7 => D = 8x-7 => R + S + M + D = 76 => 7x-7 + 6x-7 + 5x-7 + 8x-7 = 76 => 26x - 28 = 76 => 26x = 104 => x = 4 => Mahesh's present age = 5x-7 = 20 - 7 = 13 years.

Answer: B) 4913 Explanation: The given series follows a pattern that, 19 x 19 x 19 = 6859 18 x 18 x 18 = 5832 17 x 17 x 17 = 4913 16 x 16 x 16 = 4096 15 x 15 x 15 = 3375 So, the missing number in the given series = 4913

Answer: B) Genes found on chromosomes Explanation: Genetic alteration probably refers to altering Genes found on chromosomes.   Genetic alteration refers to altering DNA sequence. Gene alteration forms genetically modified products that modifies the gene sequence.   Genetic engineering, also called genetic modification or genetic manipulation, is the direct manipulation of an organism's genes using biotechnology.

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) 56 Explanation: (Total numbers of cubes in a line  x  Number of stack / tower) + ... = (6x1)+(5x2)+(4x3)+(3x4)+(5x2)+(6x1) = 6+10+12+12+10+6 = 56

Answer: A) Cell Explanation: The intersection of a column and a row in a spread sheet is called as a cell or a bon.