What Is a Planetary Nebula

Multiple Choice

What is a planetary nebula?

A) the expanding shell of gas that is no longer gravitationally bound to the remnant of a low- mass star
B) the expanding shell of gas that is left when a white dwarf explodes as a supernova
C) the molecular cloud from which protostars form
D) a disk of gas surrounding a protostar that may form into planets
E) what is left of its planets after a low- mass star has ended its life