A particular guitar string has a length of 64.0 cm, and a mass per unit length of 2.00 grams/meter. You hear a pure tone of 720 Hz when a particular standing wave, represented by the animation above, is excited on the string. Calculate the wavelength of this standing wave.

m

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 =

the answer is c. the lower legs are levers, and the knees are fulcrums. the ankles hold the loads.