Why does a comet grow a bright tail as it comes near the Sun?

1. A comet is an icy, dusty object that spends most of its time far from the Sun. 2. Out there it is cold, small and far too faint for us to see. 3. As its orbit brings it inwards, the Sun warms it strongly. 4. The heat evaporates its ices and frees the dust that was locked in them. 5. That escaping dust streams away and forms the bright tail we see from Earth. 6. Some dust tails stretch for millions of kilometres. 7. Nothing burns and no metal shell is involved, so those options are wrong. _Source: Siyavula Natural Sciences Grade 8 (CC BY 4.0), Comets and the Oort Cloud_