What is a gene?

a. the different forms of a trait

b. a segment of dna that is the basic unit of heredity

c. the appearance or characteristics that are seen in an organism

d. an organism's allele combination

Gene is the appearance or characteristics that are seen in an organism, It is also an organism's allele combination and a segment of DNA that is the basic unit of heredity

Explanation:

Gene is defined as a unit of heredity by which genetic information is transferred from parents to its offspring. The genes are present on the chromosomes as bead-like structures. Genes are made up of  DNA sequence which dictates specific protein to be made in organisms. Genes are responsible for all the inherited characters in an organism.

the answer to your question is:

c. complementary base-pairing

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