How many resonance structures or isomers does ch4 have?

Zero.

Explanation:

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As long as methane has hydrogen atoms all around the carbon atom sharing four valance electrons to attain the octate in a tetrahedral structure, no matter where the hydrogens get moved, its molecular arrangement will always have the same Lewis structure or 3D projection (attached picture) in this manner, it does not have any resonance structures.

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nacl is added to the aqueous of what? ? in order to get a proper answer you have to specify the exact composition of the aqueous solution.

the earth would become to overheated and everything alive on it will eventually die from overheating. plants will eventually die as well, water will evaporate, and it will be nothing but a hot planet without anything living on it.