What might you be doing if you measure your heart rate and find that it beats 100 times in a minute?

Rigorous exercise

Explanation:

For your heart rate is been around 100 bpm you should be doing a rigorous exercise . but if ain't doing any rigorous exercise and your heart rate is constantly above 100 bpm you should consult your doctor.

An average heart is between 60 bpm to 100 bpm.

d is the correct answer

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 =