B) compound.
A compound is usually made up of different Elements, a compound is likely to have a melting point as well.
From context clues, I believe the correct answer is B) Red Dwarf!
Vs - velocity on beginning
ve - velocity on ending. You've got:

So he needed 4 second.
Instantaneous impulse and continuous force: these are the foundations of Newton laws. In short explanation; concept of force and mass.