In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Q: Problem: a man can row a boat at 10 kmph in still water and the speed of the stream is 8 kmph . what is then time taken to row a distance of 90 km down the stream ? 
Options: a ) 8 hrs , b ) 5 hrs , c ) 15 hrs , d ) 15 hrs , e ) 20 hrs

A: b
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Q: Problem: a train running at the speed of 60 km / hr crosses a pole in 6 sec . what is the length of the train ? 
Options: a ) 356 , b ) 278 , c ) 127 , d ) 100 , e ) 150

A: d
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Q: Problem: working alone , a can complete a certain kind of job in 3 hours . a and d , working together at their respective rates , can complete one of these jobs in 2 hours . in how many hours can d , working alone , complete one of these jobs ? 
Options: a ) 2 , b ) 4 , c ) 6 , d ) 8 , e ) 10

A:
c
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