To determine the melting point of the unknown substance based on the given options, we need to look at the temperature range where the substance changes from solid to liquid.
Since the options are:
- 140°C
- between 35°C and 70°C
- 70°C
- between 70°C and 140°C
The melting point is the temperature at which the substance changes from solid to liquid.
If the heating diagram shows a transition from solid to liquid occurring within the range of 70°C and 140°C, then the melting point would be identified as being within that range.
Since we lack the actual diagram, the best assumption based on the options you've provided would be "between 70°C and 140°C" if the melting occurs during that range.
If the transition point is not clearly defined between 70°C and 140°C, and you are looking for a specific value indicated, then you may choose "70°C" if the transition appears to initiate at that temperature.
Please clarify if there are any additional details or specifics that would assist in honing in on the answer!