Answer: 2. cannot be an element.
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper 
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: methane 

Thus as it can be decomposed into its constituent elements, it is a compound.
Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present.
Thus methane cannot be an element.
The answer is 2
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Answer:
3
three half-filled orbitals each capable of forming a single covalent Bond and an additional lone - pair of electrons
In a saturated solution, extra solid X would remain solid, dissolve in an unsaturated solution, and crystallize in a supersaturated one.
A solution is said to be saturated when there is a maximum amount of solute present that has been dissolved in the solvent. As a result, the system is in an equilibrium between the dissolved and undissolved solutes: A solution is considered to be unsaturated if the solute concentration is less than the equilibrium solubility. A supersaturated solution is one that has more solute than is necessary to generate a saturated solution at a given temperature.
Learn more about Supersaturated here-
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Answer:
A
Explanation:
Definitely not in the cell theory