1. in a series circuit, as light bulbs are added, the voltage at the battery increases/decreasees/remains the same
2. in a series circuit, as light builbs are added, the current at the battery increases/decreases, remains the same.

it is a negative acceleration

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 =