Valerie hypothesizes that frogs lay more eggs in warm water than in cold water. When Valerie designs her experiment, what should be the only variable that changes?
A.
frog species
B.
time of year
C.
water temperature
D.
water flow rates

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answer: accepted answer: aquatic animals use the oxygen dissolved in water to carry out respiration. since the amount of dissolved oxygen in water is low as compared to the amount of oxygen in the air, therefore the rate of breathing in aquatic animals is much faster than it is in terrestrial animals.

explanation:

answer: the correct option is d. enzyme

lactase and carbonic anhydrase are the examples of enzymes.

lactase is an enzyme, which is present in the small intestine of mammals. it in the digestion of the disaccharide, lactose ( milk sugar) by converting it into two monosachharide, which are glucose and galactose.

carbonic anhydrase is present in the red blood cells. this enzyme plays significant role in the transport of co₂. it in the conversion of co₂ and h₂o into carbonic acid, which is then dissociated into bicarbonate ions and hydrogen ions.