Some researchers have proposed that the human population was reduced to fewer than 10,000 individuals as a result of a catastrophic event that occurred about 50,000 years ago, and that all modern humans are descendants of this small population. If this proposal is true, it would be an example of .

The correct answer is bottleneck effect.

Explanation:

The phenomenon of bottleneck effect takes place when some natural events like a tsunami or an earthquake result in the destruction of the majority of the population and leave behind some to survive. Due to the bottleneck affect the genetic diversity within the population gets reduced drastically as the majority of the population gets perished, this results in the eradication of some of the genes from the population, while the left genes are passed onto the next progenies.  

The bottleneck effect results in the generation of the new population as the leftover individuals further inbreed and give rise to a new population comprising the leftover genes. It is not necessary that the left genes passing on to the next generation are better than the one, which got eliminated, as the left genes have got selected by chance. Thus, it can be concluded that the given case is an illustration of the bottleneck effect.  

it enhances antibody production by t cells of the adaptive immune system.

hope i'm right

explanation:

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.