Suppose you are investigating how the diet of hamsters affects how much they run on their hamster wheel. in order to control the experiment, which of these should you do?
a.
change only the diet of each hamster.
b.
give all the hamsters the exact same diet.
c.
only allow some hamsters to run on the wheel.
d.
compare the behavior of hamsters and gerbils.

A. Change only the diet of each hamster.

Explanation:

If you want to know the relationship between the hamsters' feed and the way they run in the wheel of their cages, you should give each hamster a different feed and evaluate the way they behave in the wheel, the speed they run, the time that run, among other factors.

You must offer a different food for each hamster to be able to compare the results, if you give the same food to all hamsters the results can be the same, so you will not be able to compare which food showed the best results and which showed the worst results.

the real answer is b. scintillation counter

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.