Physics
On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because:

cohesion of mercury is greater than its adhesion with glass.
mercury is a metal.
cohesion of water is greater than its adhesion with glass.
density of mercury is greater than that of water.

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Physics
In the gamma decay of a nucleus

The mass number of the nucleus changes whereas its atomic number does not change
The mass number of the nucleus does not change whereas its atomic number changes
Neither the mass number nor the atomic number of the nucleus changes
Both the mass number and the atomic number of the nucleus change

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