Final answer:
Gregor Mendel's work concluded that traits are inherited independently due to genes, which occur in pairs of alleles. Both dominant and recessive alleles are passed on, disproving that only dominant traits are inherited or environmental factors solely determine traits. Therefore, the correct option is A.
Step-by-step explanation:
From Gregor Mendel's experiments with pea plants, the statement that can be concluded is: Traits are inherited independently. Mendel's foundational work in genetics revealed that traits are controlled by discrete units termed genes, which occur in pairs. Each parent contributes one allele for every gene, leading to the inheritance patterns. Traits are passed from parents to offspring with the segregation of alleles during gamete formation and the principles of independent assortment. Mendel's experiments showed that both dominant and recessive alleles are transmitted to progeny, not just the dominant ones. Thus, genes are indeed implicated in inheritance, and although environmental factors can influence the expression of traits, they are not the sole determinants.