Нужно вставить предлоги, которые в скобках.
What will you do if your chocolate falls
(on, of, out) the floor?
Will you pop it (in, into out of) your mouth?
This is often the case but people forget (around, about, of) the bacteria that are all (in, between, around) us.
The solution (about, to, from) the problem is not as simple as you might have thought until now.
The point is that instead of fighting (for, to, against) the infection, some microbiologists insist (on, about, up to) contacts with microbes to boost immunity.
You may be amazed (at, thus, that's why) the amount of germs left on your hands after washing them without soap.
Mind that we are taking bacteria (in, put, on) even through our skin.
This means that we can't hide ourselves (off, from, out of) micro-organisms and it is practically impossible to keep the bacteria (off, from, out of) our houses.
However, there is no point (of, about, in) doing so because contact with dirt contributes (to, in, into) our immune system.
This being said, wash your hands regularly (with, by, of) soap because outbecause out of every 9,000 bacteria your (under, over, inside) fingernails, 7,000 are harmless but the remaining 2,000 are extremely virulent