Answers

2015-11-02T23:08:20+05:30
Petroleum is called liquid gold because it is very costly liquid and gold is very costly metal.So, they are compared with each other.
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2015-11-03T00:04:27+05:30
Petroleum is called "liquid gold" because it is costly and is needed in a large amount i.e. day by day need of humans.
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