the choroid plexus a. cushions the brain b. forms the cerebrospinal fluid c. is another name for the ventricles d. protects the brain from infection

b. forms the cerebrospinal fluid

Explanation:

Choroid plexuses are part of the central nervous system and are located near the ventricles. They have as their main function the secretion of cerebrospinal fluid, which is the damping fluid for the cerebral cortex and spinal cord. Unfortunately, choroid plexuses are susceptible to the appearance of tumors, but most of these tumors are benign and can be surgically removed.

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation: