Answer:
The first bullet point is correct
Explanation:
The cell membrane controls what comes in and out of the cell, it needs minerals so would not block them completely, and water does not enter cells so it is clearly the first one.
No they cant be mechanical because then something would have to generate their rays through the inventing of a machine.
Answer: To do different kinds of jobs
Explanation:
We would not be able to live without it! It sustains life as we know it!
