The answer is B.
A cannot be the answer is melting is a physical change. No chemical reaction took place.
B is the answer as it is a EXOTHERMIC REACTION so heat will be given off.
C cannot be the answer as dissolving is basically atoms becoming ions, not a chemical reaction whereby a reactant reacts with another reactant to form a product.
D cannot be the answer. Same reason as for why A is not the answer.
Cheers.

But

- Hence higher the radius lower the voltage
- Lower the voltage higher the capacitance .
<h3>100cm diameter having aluminium sphere has a larger capacitance</h3>
Technically you can go forever on and on, but maybe your question was like how many rotations in a certain distance?
Highlighter, color coding sections that go together, flash cards, relaxing with someone while they read out questions ( this will help with testing anxiety too). If you get distracted easily use games to study or small sayings instead of the usual white and black sheet of paper.