Wait this is highschool biology?!
Woah... thought it would be harder....
Anyways, see "micro" means really small, so small that your bare eyesight can't take it (or see it, I don't care). A microscope was meant to see things that our eyes can't. Since humans cant see microlife we use a microscope.
Mind Blown...
Eat plenty of protein at every meal eating food can increase your metablisome. for a few hours or cold water do a high intensity workout lift heavy things stand up more drink green tea or orally T eat spicy foods get a good night sleep
I think the answer is (4) using large amounts of some materials that cannot be renewed :))
i hope this be helpful
* happy new year *