When a rehabilitation area is established at the scene of a multiple-casualty incident, it should: ?

be in a location that prevents visualization of the scene itself.

Explanation:

When a rehabilitation area is established at the scene of an incident with multiple victims, some precautions must be taken to ensure the safety and less psychological impact of those there. One of the precautions that must be taken is to establish the rehabilitation area in a place that prevents the viewing of the scene itself, preventing a panic outbreak that harms people.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

that is wrong, its not thymus.