If all the light waves are absorbed by an object then the object will appear a) black b) brown c) gray d) white

A) Black

If it absorbs all light it does not emit or reflect any, meaning the object will appear black

answer; (arch); good luck

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 =