Answer: D) Any one pair of A and B, B and C or C and A is sufficient Explanation: Let distance between A & B = d kmLet speed in still water = x kmphLet speed of current = y kmph from the given data,d/x = 2 From A) we get dFrom B) we get d/x+yFrom C) we get y   So, Any one pair of A and B, B and C or C and A is sufficient to give the answer i.e, the speed of upstream.

Answer: C) Romans Explanation: Romans (753 BC - AD 410) began public health and sanitation systems.   Romans established the first public health and sanitation systems by building sewers and aqueducts. They also treated diseases with diet, exercise and meditation.

Answer: B) Electron transport chain Explanation:

A Windmill.

Answer: A) contains fluoride to harden the tooth enamel Explanation: Saliva is produced by the salivary gland which helps in food digestion.   Option A) contains fluoride to harden the tooth enamel is not the function of saliva.

Answer: D) 5 Explanation: Arithmatic mean = sum/members  => (1x1 + 2x2 + 3x3 + 4x4 + 5x5 + 6x6 + 7x7) / (1 + 2 + 3 + 4 + 5 + 6 + 7) => 140/28 = 5

Answer: A) 4096 Explanation: Here given series follows a pattern that 0.25, 8, 128, 1024, ? 0.25 x 32 = 8 8 x 16 = 128 128 x 8 = 1024 1024 x 4 = 4096

Answer: A) 14 days Explanation: Let A worked for x days. x/21 + 4/28 = 1  => x = 18   A worked for 18 days. So, A can complete the remaining work in 18 - 4 = 14 days.