Scientists think that dolphins and whales may have evolved from a common ancestor. Fossils have been found showing how this organism slowing evolved into the seperate organism. These fossils are know as A.
Index Fossil

B.
Dervied Fossil

C.
Avada kedarva Fossil

D.
Transitional Fossil

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 =