Famine- High population means more mouths to feed
Disease- Diseases usually spread more quickly with people who live closer( as it can just move from one person to the other)
War- People like to fight for land, resources, money, etc. And having more of those things mean they are more able to support families, communities, and more.
(Hope this helps a little)
One advantage of genetic engineering is the production of valuable proteins: recombinant DNA made possible the use of bacteria to produce proteins of medical importance such as genetically engineered human insulin which is of great importance.
Another advantage is the production of vaccines. Vaccines produced by genetic engineering offer an advantage that the microbial strains from which proteins are extracted do not contain complete viruses and thus there is no risk of accidental inoculation with live virus.
The answer may be B due to they mostly look dark :3 hope I helped