I think it might be B but I am not sure
Answer:
When the propagation of an infectious disease gets reduced, people stop getting their children or themselves getting vaccinated for the infectious disease.
But what we forget is somebody out there might be an asymptomatic carrier of the disease and can spread the disease. As a result, if many people are not vaccinated for the particular disease, then there might be an outbreak of the infectious disease again and it can be deadly.
D - Allow pH to change drastically.
The reason that we have buffer in our system is to protect AGAINST sudden change of pH
Overproduction
Most species produce more offspring than can survive.
Competition
Since living space and food are limited, organisms must compete for the necessities.
Variation
Differences between individuals in a population.
Adaptations
Any kind of inherited trait that improves an organism's chances of survival.
Natural selection
The environment selects organisms with optimal traits to be the parents of the next generation.
Speciation
Over many generations, favorable adaptations accumulate and may result in a new species.
Outer membrane or plasma membrane, cytoplasm, nucleus, ribosomes,