What causes the electrons to move and form static electricity? 1) contact with a battery
2) an open switch
3) contact between two substances
4) moist air

mistakes are ok

it doesn't. it was imagined up in the middle ages.

i would say

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =