Sian wants to measure the number of seconds that it takes for the contents of a beaker to change from clear to purple. Which of these tools should she use for this purpose?

i think the answer is a and b

i wish you luck

e/c, where e is its total energy

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 =