Why does the temperature of ice remain constant during the melting of ice?

Correct option is C

The correct answer is (c) Heat is used to break the bonds between molecules

Explanation:
• When any standard solid substance like block ice is constantly heated, its internal temperature gradually and predictably increases until it firmly reaches its specific exact melting point (0°C).
• During the highly active physical phase transition moving straight from solid ice to liquid water, the temperature remains perfectly incredibly constant even though thermal heat energy is continuously being supplied.
• This specific supplied heat energy is now being entirely consumed purely to overcome the strong intermolecular forces of attraction forcefully holding the ice particles rigidly in their fixed crystal lattice.
• Because this exact thermal heat practically does not raise the active kinetic energy (and thus clearly not the temperature) of the particles, it is considered physically "hidden" and is scientifically formally known as the Latent Heat of Fusion.
• Only totally after absolutely all the solid ice has completely physically melted into fluid liquid water will the overall temperature of the entire system finally begin to slowly rise again.

Information Booster:
• The precise measured latent heat of fusion of normal ice is exceptionally unusually high, specifically officially measured at an impressive $3.34 \times 10^5 \text{ J/kg}$.
• Explicitly due to strictly absorbing this hidden heat, particles moving freely in liquid water precisely at 0°C actually physically possess significantly much more total energy than particles locked solidly in ice at the exact same identical temperature.

Additional Knowledge:
Ice absorbs heat but does not melt (Option a)
• This statement is physically obviously incorrect; the very physical process visibly occurring rapidly during this exact phase is indeed the rapid melting of the solid ice.

Ice becomes denser (Option b)
• While liquid water is indeed naturally famously denser than solid ice, this odd density change is merely a structural consequence, absolutely not the thermodynamic physical reason the temperature stays incredibly constant.

Ice reflects heat (Option d)
• While a bright white ice surface does have a naturally high albedo and can obviously reflect some radiation, this simple optical property absolutely does not begin to explain the perfectly constant temperature reliably observed during a fundamental massive phase change.

So the correct answer is (c)