Question

a supernova may leave behind a dropdown which is the size of a large city. when the outer portion of a red gcut offd is blown away, a dropdown is left behind. the most-massive stars may beccut off dropdown (options: neutron star, white dwarf, black hole), which are not directly detectable

Explanation:

1. A supernova (from massive star explosion) leaves a neutron star (size of a large city, dense remnant).
2. Red giant's outer layers blown off leave a white dwarf (remnant of low - mass star evolution).
3. Most - massive stars become black holes (gravity so strong, not directly detectable).

Answer:

First blank: neutron star
Second blank: white dwarf
Third blank: black hole