If two objects have exactly the same melting points, are they same substance?

most object has a slightly different melting point from each other so if the melting points are same it is much more likely to be the same object.

A same object however could have a variation in the melting point due to the slight change in its composition (alloy)

c is the answer because when something is left after something evaporates that shows the chemical change.

warm front forms when a moist, warm air mass slides up and over a cold air mass. as the warm air mass rises, it condenses into a broad area of clouds. a warm front brings gentle rain or light snow, followed by warmer, milder weather.

hope i !