Final answer:
Traits conditioned by multiple loci contributing to variable phenotypes and affected by environmental factors are called quantitative traits (option 2).
Step-by-step explanation:
The traits that are conditioned by multiple loci and form continuously variable phenotypes that are conditioned by both the genotypes and environmental influences are most appropriately termed quantitative traits. These traits, such as height or weight, can be measured and show a wide range of variability. They are also influenced by environmental factors and are commonly polygenic, meaning that multiple genes contribute to a single trait. This contrasts with Mendelian traits, which are typically determined by a single gene locus and have discrete categories or classes (e.g., violet or white flowers in pea plants).