Astar may form a black hole once it cannot a. maintain a high enough temperature relative to its own gravity. b. continue to rotate on its axis due to its increasing mass. c. evolve into a supergiant. d. grow any larger.

The answer is A, becasue the tmperature cannot be maintianed due to the amount of iron building up in the core of a star large enough to collapse into a black hole and iron cannot generate energy when it is fused it takes it. the the star's fussion slows to the point where gravity takes over and the star collapses in on itself creating a black hole.

The answer is orbit around nucleus

Letter a, because when there are unlike charges they will always attract to each other.