1. Black holes result from the stars that are initially at least:
half the mass of the Sun
twice the mass of the Sun
eight times the mass of the Sun
25 times the mass of the Sun
2. The Helix and Egg nebulae are
supernova remnants.
planetary nebulae.
the result of carbon detonation.
the result of the collapse of the iron core of each star.
nebulae associated with Herbig-Haro objects.