Respuesta :
Answer: Option (A) is the correct answer.
Explanation:
It is given that the unknown substance is solid at 15 degree celsius. When further heated then heat energy breaks the bond between molecules of the solid.
As a result, temperature remains constant until all the bonds are broken down to convert the solid into liquid.
Hence, the constant 17 degree celsius temperature shows that the solid is melting and after it completely melts then it converts into liquid at 23 degree celsius.
Thus, we can conclude that the statement its melting point is 17 °C, is correct about the unknown substance.
The correct answer is A. 17 degrees Celsius
The reason why is because the temperature in degrees Celsius for it to turn into a solid is 23 degrees and it isn't quite 23 degrees but not so little it will barely do anything to it at all.