Which statements about the formation of the solar system are true and in a correct order?

a.
a black hole collapsed to form the sun; small planetary objects formed; small planetary objects collided with each other to form larger objects.

b.
most of the dust and gas contracted into a central mass—the sun; half the mass of the cloud condensed to form jupiter; asteroids and comets crashed into the sun to form the smaller planets.

c.
a spinning cloud of dust began to compress to form the sun; small planetary objects formed; hydrogen and helium became concentrated in the outer solar system to form the outer planets.

d.
gravitational force held the newly formed planets around the sun; small planetary objects formed; hydrogen and helium became concentrated in the outer solar system to form the outer planets.