Question given below is followed by three statements. Study the question and the statements. Identify which option is necessary to answer the question.

The mean temperature of Monday to Wednesday was 37 degree Celsius and of Tuesday to Thursday was 34 degree Celsius. What was the temperature on thursday?

I. The temperature on Thursday was 4/5th that of Monday
II. The mean temperature of Monday and Thursday was40.5 degree Celsius.
III. The difference between the temperature on Monday and that on Thursday was 9 degree Celsius.