It has a job similar to a police officer who allows select people to enter and leave a crime scene.
Explanation:
The primary purpose of the cell membrane is to preserve the cell from its surroundings. The cell membrane manages the movement of materials in and out of cells and organelles. In this form, it is selectively perforable to ions and organic molecules. It is the same as of police officer or security guard that check the people and allow only a few to enter a specific place.
I am almost entirely sure that DNA testing had not been discovered at this time, but regardless of whether that is true, the very first criminal case that DNA testing was used in occurred in 1985. So no, it was not used commonly in the 20's.
Answer: An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. i think its B
