Que estudia la geografía ?

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