The purpose of the system is to prevent foreign substances from entering the body and to attack foreign substances that are in the body.
A. immune
B. endocrine
C. nervous
D. excretory

Immune

Explanation: The immune system is the body's defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease. The immune system is made up of a network of cells, tissues, and organs that work together to protect the body.

regulation of gene expression. gene expression can be regulated by various cellular processes with the aim to control the amount and nature of the expressed genes. these regulatory proteins bind to dna and send signals that indirectly control the rate of gene expression

explanation:

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.