Physics
Holography is a technique of

Recording a permanent three dimensional photograph of a given single colour or a multicolour
Recording a permanent three dimensional multicolour photograph
Recording a permanent, sharp two diimensional black and white or multicolour photograph
Recording a permanent three dimensional black and white photograph

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Physics
Conservation of energy refers to the fact that

Energy cannot be created or destroyed but can be converted from one form to another
If you conserve energy you will not be as tired
The entropy of the universe is always increasing
No chemical reaction is 100 percent efficient

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