Earth's magnetic field is created by the bar magnets reaction forces gravitational forces flow of electric charges

The correct option is;

Flow of electric charges

Explanation:

The movement of the enormous quantities of molten metals in the Earth's outer core generates electric current which travel several thousands of miles per hour due to the axial rotation of the Earth results in the metallic particles being lined up and generating very strong magnetic fields (due to dynamo effect) that extends all over the planet and into space.

they may bind directly to special “promoter” regions of dna, which lie upstream of the coding region in a gene, or directly to the rna polymerase molecule.

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