Which of the following air conditions would be least likely to have precipitation? a. warm, dry air b. warm, moist air c. cold, moist air d. cold, dry air

C

Explanation:

when it's cold,the water vapour that atmosphere can hold is much lowerand when moist air have so much water vapour in it...perfect condition for precipitation

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 =

snell's law

refractve index = sin incidence / sin refraction