Which microorganisms causes tooth decay?

Streptococcus mutans.

Explanation:

Streptococcus mutans is the bacteria (it is still a microorganism) that predominatly causes tooth decay. It is present in all areas of the mouth.

ionic bonds are two oppositely charged ions that attract. a sodium ion has a 1 positive charge; a chloride ion has a 1 negative charge. sodium and chloride have oppostive charged ions that attract which forms an ionic bond. a chemical bond formed when two atoms share electrons is called

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.