Give the name, and explain the function of nerve cells. Approximately how many of these nerve cells make up the brain?

Cells of the nervous system, called nerve cells or neurons, are specialized to carry "messages" through an electrochemical process. The human brain has approximately 86 billion neurons.

answer: a. a gene that causes a specific trait.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.