Which one of the following is a decomposition reaction?

a. 2h2o (l) → 2h2 (g) + o2 (g)
b. n2 (g) + 3h2 (g) → 2nh3 (g)
c. ch4 (g) + 2o2 (g) → co2 (g) + 2h2o (g)
d. 2h2 (g) + o2 (g) → 2h2o (g)

so easy. just google the electromagnetic waves and it’ll pop up.

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 =