Which of the Following Is True Regarding Planetary Nebulae

Multiple Choice

Which of the following is true regarding planetary nebulae?

A) Some are spherical, but most have bipolar structure.
B) They are the result of the mass loss during the main sequence stage of the most massive stars.
C) They are the rings of material surrounding newly formed stars that will eventually form theplanetary systems.
D) They are the ejected envelopes of highly evolved brown dwarf stars.
E) They are the coronas surrounding most blue stragglers.