Two students are holding opposite ends of a spring in a classroom. One student stands on the left end of the classroom and the other stands at the right end. They shake the spring so that a longitudinal wave travels along the spring. In which directions will the longitudinal wave oscillate?

the second one and the forth one are in the purple because they are opinions and the rest are in the yellow

explanation:

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 =