Here's a problem to solve: A teacher gives a student an unknown liquid and wants the student to find the boiling point of the liquid. The student performs the investigation and finds the boiling point is 50°C and then repeats the experiment and finds the boiling point is 70°C. How should the student best identify the boiling point?

Among the 4 following options, which is the correct answer?

- A: use the second boiling point
 
- B: average the two numbers
 
- C: use the first boiling point
 
- D: repeat the investigation
 