Which hypothesis most likely explains the results at 60°c and 70°c?
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a. the substrate has been used up because of the high temperature,
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b. the enzyme has changed shape because of the high temperature.
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c. the enzyme is only effective at very high temperatures,
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d. the bonds in the substrate are weakened at high temperatures

The correct answer is option B.

Explanation:

At 60 to 70 degrees the reaction stops, due to the rise of temperature more than its optimum temperature. At high-temperature molecules of enzyme vibrate more, this vibration breaks the bonds that determine the shape of the enzyme in shape.

The shape of the active site of enzyme changes due to this and the substrate is not fit together with it and the reaction stops.

Thus, the correct answer is - B.

where is the scientific experiment?

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.