Which of the following lists the correct requirements for a black hole to form?
a. the star must be 10 to 28 times larger than earth's sun, and a supernova explosion must have occurred.
b. the star must be 10 to 28 times larger than earth's sun, and a supernova explosion must not have occurred.
c. the star must be 29 times larger than earth's sun, and a supernova explosion must not have occurred.
d. the star must be 29 times larger than earth's sun, and a supernova explosion must have occurred.