B) compound.
A compound is usually made up of different Elements, a compound is likely to have a melting point as well.
Answer:
A) 3.11 Hrs
Explanation:
Wave speed is given by the formula

now we will have


now the time taken by the wave to move the distance 560 km is given as



t = 3.11 hours
The third one.
The nucleus of an atom is made up of protons and neutrons. Protons and neutrons have the same relative mass (rounded to 1). Electrons have an extremely small mass.
Therefore, the particles in the nucleus are more massive than those in the electron cloud.