A takes 4 days to do a work. B takes twice as long as A. C takes twice as long as B and D takes twice as long as C. They are made in groups of two. One of the groups takes two third of the time taken by second pair. What is the combination of the first pair?

A,C

A,D

B,C

B,D

Correct Answer : B

The length of the bridge which a train, 130 metres long and travelling at 45 km per hour, can cross in 30 seconds, is