Answer:
D.
Explanation:
But this just happen for big stars, like more than 20x the Sun mass.
Shortly: A nebula is a cloud of gas and dust, the material starts to be acummuleted and became a protostar (is like a big planet, almost a star). With enought mass this is a star, burn hydrogen and transform it in Helium.
This occurs in Main Sequence, is about almost all the life time of a star. Then starts the lack of hydrogen. Gravity compress everything, pressure goes up and heat all. Too much energy, Helium get burned and the star grews fast, became a Red Giant. Time pass and the fuel is over, no more making fusion, gravity compress the star, too much strenght, colapses, neutron star.
If it have pretty mass, ok. If have more than like 2x Sun mass, became a blackhole.
Their called rafts they lay them by surface of stagnant water
Answer:
1.2826 x 10^-13 m
Explanation:

Here, k be the kinetic energy and m be the mass
K = 50 KeV = 50 x 1.6 x 10^-16 J = 80 x 10^-16 J
m = 1.67 x 10^-27 kg

λ = 1.2826 x 10^-13 m
They actually DO have velocity limits. There are legal restrictions on both speed and direction.
-- Speeds are limited according to the black numbers on white signs that you see on sign-posts everywhere.
-- Directions are limited by the layout of the pavement and curbs on all the highways, avenues, roads, boulevards and streets, as well as the countless signs that say "One Way", "No Left Turn", "Keep Right", "Keep Left", etc. Violate one of these, and you get nailed as sure as if you had exceeded a posted speed limit.