Which best describes the pure lines in mendel experiment

The propositions are:
A. They were the F2 generation
B. They were heterozygous 
C. They were homozygous
D. They could not reproduce

The right answer is: C

Mendel's laws are three laws concerning the principles of biological inheritance. The rediscovery of Mendel's laws in 1900th, and their combination with the discovery of chromosomes, considered as the physical medium of heredity, is at the origin of the foundation of formal genetics at the beginning of the twentieth century.
Homozygote is a gene that, in an individual (animal or plant), will be represented by two identical alleles on the same locus.In genetics, we speak of a pure strain for a breeding population identical to itself, generally, a population where each individual has the same genotype and each gene is homozygous. The pure strain, obtained in the laboratory, consists of homozygous individuals.
Homozygosity is opposed to heterozygosity.