Answer:

Explanation:
Hello,
In this case, the increase in the temperature involves the addition of heat that is defined in terms of mass, heat capacity and temperature:

In this case, the heat capacity of iron is 0.450 J/(g*K), thus the heat results:

In such a way, since the temperature is increased heat is added, that is why it is positive.
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Precipitation reaction and double displacement reaction
C.
It is the only thing that is making a new thing, and not breaking or taking apart something that is already there.
Solar energy is so promising option as it is having very low operational cost but still it is not being used optimally throughout the world.