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.

Q: Problem: in 10 years, a will be twice as old as b was 10 years ago. if a is now 5 years older than b the present age of b is
Options: a. 37, b. 38, c. 39, d. 35, e. 41

A: d
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Q: Problem: it is only in the second option we find the sentence a in continuation with the opening sentence d. sentence a alone explains, why the fear has such enormous effect on the human beings.
Options: a. 28, b. 99, c. 728, d. 27, e. 271

A: b
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Q: Problem: the ratio between speed of the two trains is 7: 8. if the 2 nd train runs 400 km in 4 hrs, what is the speed of the 1 st train ?
Options: a. 87.9, b. 87.5, c. 87.7, d. 87.6, e. 43.3

A:
b
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