Control groups are useful in scientific experiments because they (1 point) Are easily identified by the experimenter during the investigation.
Are cheap and relatively easy to maintain throughout the experiment.
Prevent the data collection from being contaminated by other variables.
Provide a standard for comparison with the data collected in the investigation,

answer: a ball

explanation: because it will bounce

in simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. this is also known as upthrust.

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 =