Human Immunodeficiency Virus -- this is HIV, the virus that causes AIDS.
Flu viruses. There are lots of different strains of flu virus, which is why new vaccines have to be made every year.
Cold virus. The common cold is caused by a virus.
The answer is B
Explanation. The density explains the amount of mass for how small or large an object is. Best way to test density is with water. If it is MORE DENSE (heavier in small area) it will sink.
Plasticity is to be molded. You can mold plastic is is bendable and heats up easily to give the advantage of being reshaped
The answer to this is C. The ancient fossils are a record of when shallow seas covered much of the united states. While the fossils are of organisms that are the precursors of many modern day organisms, changes in ocean geography and other factors eventually caused those older species to become extinct.
