Answer:
B) Styrofoam is a good insulator.
Explanation:
When talking about thermal energy, or a heat, insulator is a material that doesn't allow heat to pass through easily. On the other hand, a conductor is completely the opposite, it allows, quite successfully, transfer of the heat.
So, regarding ice cream, from these definitions above, we can conclude that insulators will prolong melting time, while, in the conductors, ice cream will melt rather fast.
Looking at the table, we see that Styrofoam had the longest melting time, which makes it quite successful insulator.