Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
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Question: Problem: in a room filled with 6 people, all 6 people have exactly 1 sibling in the room. if two individuals are selected from the room at random, what is the probability that those two individuals are not siblings ?
Options: a. 3 / 5, b. 4 / 5, c. 5 / 6, d. 5 / 12, e. 7 / 12

Answer: b


Question: Problem: a man goes downstream at 10 kmph, and upstream 8 kmph. the speed of the stream is
Options: a. 0 kmph, b. 4 kmph, c. 1 kmph, d. 2.5 kmph, e. 26 kmph

Answer: c


Question: Problem: the annual birth and death rate in a country per 1000 are 39.4 and 19.4 respectively. the number of years x in which the population would be doubled assuming there is no emigration or immigration is
Options: a. 20, b. x = 25, c. x = 30, d. x = 35, e. 40

Answer:
d