Hi,
The answer should be C.
Hope this helps, if you’d like further explanation please let me know.
Explanation:
When conducting a melting point experiment, if we were to heat a sample quickly. Large amount heat is provided instantly which would melt the crystals in the tube very quickly, even before the temperature of the thermometer reaches to that level. So the observes melting point would be much lower than the actual melting point when sample is heated slowly.
Answer:
helium is the smallest element and francium is the largest
