A(n) is a mass of living protoplasm.

amoeba

paramecium

euglena

virus

The correct answer for the blank is-

amoeba.  

Protoplasm is considered as the living part of cell, which includes cell membrane, cytoplasm, and the nucleus.

Amoeba ( it is a protozoan, which is a group of kingdom protista) is the simplest living form of unicellular eukaryotic organisms. It does not have any specified shape. All the cellular activities that are essential for its life, takes place in the protoplasm. As all the properties of protoplasm can be readily observed in this simple organic form ( Amoeba), therefore, it is considered as the mass of living protoplasm.

beta is electron from nucleus

something from nucleus has changed, but charge must be same for cons of charge

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 =