The correct answer is fixed migration pattern.
Extinction means termination of last member of a particular species. This can be due to various factors. The reason could be natural or human interventions. The best characteristics of an organism to be less likely to face extinction are the fixed migration pattern. Migration of that particular species in a fixed pattern will make them adapt different environment. This saves the species from natural extinction. Even if the species of a particular geographical area dies the migrated species will be alive to breed and save the species from extinction.
The building blocks are amino acids
After crystal violet staining, the Gram-positive bacteria may appear dark blue or violet. The cell wall of gram positive bacteria have thick peptidoglycan layer, thus it retains the crystal violet stain compared to gram negative bacteria.

Actually Welcome to the Concept of the Genes.
Basically a Polygenetic trait is controlled by two or more genes.
Examples of human polygenic inheritance are height, skin color, eye color and weight. Polygenes exist in other organisms, as well.
Answer: It is b multiple alleles
Explanation: Alleles determine your genes.