Embryo should be the answer
"REPRODUCTIVE ISOLATION" needs to occur for speciation to happen.....
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.
I cannot see the imagine very well would you mind taking another?
Answer: D.
Explanation:
Viruses can be cultivated within appropriate hosts, such as a living cell . For example, bacteria are grown in an acceptable growth medium to research bacteriophages; then bacteriophagi are added. Within the bacteria, the bacteriophages replicate and greatly increase their numbers.
Diploid cell lines (or strains) are subcultured approximately 100 times before death. A lot more useful in the laboratory and they can be kept in liquid nitrogen forever. The human embryonic fibroblasts are one example of this kind.
As diploid cell line, developed from human embryos have more accurate results and can be stored for longer period of time, they are widely used in cultivation and isolation of viruses that require human hosts.
Hence, the correct option is D.