Final answer:
A 50 degrees reading on a Celsius thermometer is halfway between the freezing and boiling points on the Celsius scale, so the answer is C. 25 degrees.
Step-by-step explanation:
The freezing point of water on the Celsius scale is 0 degrees Celsius (°C). A 50 degrees reading on a Celsius thermometer is therefore 50 degrees above the freezing point. Since the Celsius scale spans 100 degrees between the freezing point and the boiling point, a 50 degrees reading is halfway between the freezing and boiling points. So the answer is C. 25 degrees.