The initial cross of two true-breeding individuals is known as the: A. Parental generation
B. Primary generation
C. F1 generation
D. F2 generation

monohybrid cross

Fertilization between two true-breeding parents that differ in only one characteristic is called a monohybrid cross. For a monohybrid cross of two true-breeding parents, each parent contributes one type of allele resulting in all of the offspring with the same genotype.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.