The Main Sequence Has a Limit at the Lower End

Multiple Choice

The main sequence has a limit at the lower end because

A) low mass stars form from the interstellar medium very rarely.
B) low mass objects are composed primarily of solids, not gases.
C) pressure does not depend on temperature in degenerate matter.
D) the lower limit represents when the radius of the star would be zero.
E) there is a minimum temperature for hydrogen nuclear fusion (the definition of a star) .