Physics
The increasing order of the refractive index of certain materials is (left to right) ________

Rocksalt, Benzene, Kerosene, Ice
Kerosene, Ice, Benzene, Rock Salt
Rock Salt, Ice, Benzene, Kerosene
Ice, Kerosene, Benzene, Rock Salt

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Physics
In a railway track, two rails are joined end to end with a gap in between them because

Accidents due to contraction in winter can be avoided
Air-gaps are necessary for bearing the weight of running train
Steel can be saved
Accidents due to expansion in summer can be avoided

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