An engineering student is studying the effects of cryogenic treatments on a particular material. The treatment involves cooling the material with specific applications of liquid nitrogen.

The answer is "choice C"

Step-by-step explanation:

Please find the complete question in the attached file.

This is because the temperature in grades Celsius, y, of material could be represented by the previous diagram, in which x is the period, in hours.

It is evident from the study that, the y-intercept is 40 degrees Celsius and thus the temperature difference is 40.

That edge of the top paraboloid is (15-200) so at most -200 ° C at 15 hours the temperature of the material. During 30 hours, the material returns to its initial temperature as the temperature at x = 30 is 40 °C.