The possibility to answer is C.
Answer - Theory
Reasoning - Your best bet and term to describe the evolution by natural selection is theory as to still scientific theory/research is still ongoing and changes can be made in a different direction.
Tight hydrogen bonding
The atoms in a compound are held together by a chemical bond. The chemical bonds can be either covalent bonds or ionic bonds. Both the bonds are considered very strong bonds. These bonds are mainly formed by sharing of electrons or in the case when one of the elements making the compound donates electron to the other element. The nucleus of each atom attracts to form a strong bond. This property of attraction between the nucleus of the atoms actually helps in forming the chemical bonds.<span>
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The cause of mutations in gene expressions are the changes of gene instructions that causes your protein to malfunction. The effect of mutations are the genes not being able to function properly and send the wrong codes/info to your cells.
Easy 5 points. Stop, Drop, and Roll. In that order.