Variations in evolution usually refers to variation of genes at a particular loci. This differs from diversity which is the total of genetic differences within a population. Speciation is the reproductive isolation of a subset of a population.
The correct answer is option A- HIV virus.
HIV virus is an example of enveloped virus, that has the ability to infect a host cell by attaching itself to it and fusing with the host cell. Once infected, the virus leaves the host cell and moves to another cells to infect them. The HIV virus contains glycoprotein spikes to attach to the host cell.
Answer and Explanation:
Multiple organisms especially those that live on land require a rigid framework to support their bodies off the ground and to maintain their shape. Skeletons also offer protection to delicate internal organs for example the skull protects the brain
