Which object made of one or more smaller units would make the best model of a group of cells from a plant?

no simpler subs form complex ones. synthesise = make

compass can be used day and night, cloudy or sunny

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 =