Final answer:
To find the new temperature after a 15°C increase, add the increase to the initial temperature. Starting at 25°C and adding 15°C, the new temperature is 40°C.
Step-by-step explanation:
If we start with an initial temperature of 25°C and increase it by 15°C, we calculate the new temperature by simply adding the increase to the initial temperature.
25°C + 15°C = 40°C
Therefore, the new temperature of the water bath would be 40°C, which corresponds to option c.