As a solid reaches its melting point intermolecular bonds have been disrupted, causing:
a: increased particle vibration
b: a change in particle position
c: breaking of intermolecular bonds
d: all of the above

Option (B) is the correct answer.

Explanation:

Melting point is defined as the point at which a solid substance changes into liquid state.

During the melting point temperature of substance remains constant until the whole solid substance changes into liquid state.

At the melting point, particles of the solid vibrate rapidly and as a result position of the particles changes from one place to another.

Thus, we can conclude that as a solid reaches its melting point intermolecular bonds have been disrupted, causing a change in particle position.

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there are no contact forces mentioned on the list of choices that you've provided.