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: what is the value of n if the sum of the consecutive odd intergers r from 1 to n equals 169 ?
Options: a. 47, b. 25, c. 37, d. 33, e. 29

A: b
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Q: Problem: a train of length 250 m crosses a bridge of length 150 m in 20 seconds. what is the speed of train ?
Options: a. 33, b. 27, c. 25, d. 22, e. 72

A: e
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Q: Problem: average marks of a, b, c is 48. when d joins average becomes 47. e has 3 more marks than d. average marks of b, c, d, e is 48. what is the marks of a ?
Options: a. 43, b. 44, c. 45, d. 46, e. 47

A:
a
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